Flibby

Really interesting replies, thank you to everyone.
The responses help with my mindset question. Really rather than thinking about setting up one SBF position to deal with an enemy position, I think i need to be thinking about a whole fireplan in order to gain fire superiority over the enemy where it counts, and then exploiting that area, making sure that enemy positions that I cannot adequately suppress are avoided until later, when hopefully a different angle opens up from manoeuvre that means i can bring forces to bear on it.
I like the idea of tactics scalling up as described by IICptMillerII. I must confess that I have focussed on platoon level tactics where I always have more than a platoon as my disposal therefore I'm thinking too small scale and trying to do the TacAI's job for it.
 

I don't see recon or scouting anywhere in your tactics there.
Generally speaking, if you have the appropriate resources at your disposal, then patience, reconnaissance, and applying firepower will work in your favor. Personally speaking, impatience is my #1 error. In your example the enemy has too many points to cover your angle of attack. Don't try and establish a base of fire on an enemy that could return fire from superior positions the second you pop your head. Smoke screen. Or apply harassing artillery support to soften them and then follow through with suppression via on-map resources. Those are just examples off the top of my head. 99% of the time if something goes sideways in CM it is, on reflection, wholly my fault and there usually was a better way. And the best way to learn is to just make those mistakes and then think about them and figure out what could have been done different.
Sometimes scenarios/campaigns are designed to be considerably more constrained, surprising, and/or difficult, but I suppose knowing the difference between "I'm messing up" and "the scenario is designed to mess me up" is a whole 'nother bag of hammers.
 

Tactics scale. Think of it like math. First you learn to count, then add/subtract, then multiply, then divide, etc. Eventually you go from 2+2=4 to [insert long equation with numbers/letters/symbols here]. 
The military (well, competent ones at least) teach everything following a crawl, walk, run style. That is, you start small and simple and build up from there. The point of those manuals is not to show you how to overcome every possible tactical situation you are going to find, but to give you the basic template that can be applied to any situation and built upon. So you are correct that a lot of the examples in the manuals are not ones that you will find out in the real world, with a few exceptions. But, when you apply the right tactical principles to situations which the manuals attempt to teach, you will be better off than not. 
Don't think you are alone here. A common anecdote from many wars is that "only newbies actually follow the manuals." That is a famous line I've heard in reference to the Vietnam War more times than I'd like to recall. Doing something "by the book" and stating that in a bad context is the same idea. When people want to learn about military tactics, most turn to manuals covering the fireteam and squad level. This is the wrong thing to do, but this is what pop culture fuels (videogames such as Brothers in Arms, while great, depicts a ludicrously oversimplified depiction of combat at the squad level) people to do. In actual warfare, squad "tactics" are irrelevant. What is more important is squad SOPs, such as "spread out enough not to all get wasted by one shell but not too far that you get lost/unsupported," and "keep track of yourself, your gear, and your team members," and "be aware of your surroundings and your own status, such as ammo and injury." In CM, all of this is taken care of for you by the TacAI. 
Here is a better way to think of tactics in CM; you always want to apply tactics from the highest level you command. What that means is, if you are in command of 1 platoon, then use platoon level tactics. If you are in command of 2 platoons, use company level tactics. If you are in command of multiple companies, then use battalion tactics. Another way to think of this is, if you have multiple elements (lets say 2 companies) what authority would be required for you, the player, to give company commanders orders? The answer would be a battalion commander, and so battalion level tactics is what you want to use. 
Tactics generally scale up, not down. If you are in an environment where you have an entire battalion at your disposal, a single platoon likely will not be able to do much on its own. This is where that scaling comes into play. If a manual depicts two platoons attacking an objective, one as the base of fire and the other as the assault, but you are commanding multiple companies, then you just upscale it all. Instead of using a platoon to fix and a platoon to flank, you swap the platoon for a company. There is a lot of nuance to that, but that is the general principle. 
A final note on manuals: most of them that you will find from a quick google search are going to be somewhat dated. The principles remain, but the nuance changes a lot. Basic infantry tactics are the same now as they were in WWII. However, the weapons of war have changed a lot since then, creating a whole different set of nuance to deal with. 
Manuals are not a bible, and by that I mean a perfect reference. Many of them are more complicated than they need to be, confusing or unintentionally misleading. For example, the manual detailing how to call for artillery is long and dense, but the actual procedure is very simple. In the case of an artillery manual, it also makes general assumptions about its reader, like the ability to already know how to read a military map and derive coordinates from one. So, sometimes manuals are missing a piece of information because it assumes the reader already knows the institutional knowledge. If you don't know what information is missing, this can complicate reading manuals even more. This is one of the many reasons why basic training exists in the first place, to create a common standard of knowledge, and why further instruction is needed to learn a given specialty within the military. 
Hopefully that helps some. 

Hopefully a platoon assault like your example would not take place unless all the information in the form of a SME order was available. If possible. Perhaps scouts already ascertained what you are up against. What's covering the enemy MG. And then the scenario starts. CM does that pretty good, you can detach the platoon MMG, set up a fire base and hook in with the rest of the platoon as you said. Hopefully you have all the useful information to read prior to battle.
That basic text book tactic is taught to infantry section commanders as well, so they have a fundamental understanding, and perhaps a qualification to control fire and movement at a higher level. Applying it to CM depends on the scenario, sometimes you get a text book operation, other times you get a wtf situation with duff intel requiring some adaptive thinking.

To me, cover does not really seem to matter that much in the CM games. It matters a bit, but it's more about fire superiority. Squads in good cover will often get blown to bits very quickly if the enemy has fire superiority. A single tank shell hitting a foxhole position or the side of a building is sometimes all it takes to wipe out the squad inside. On the other hand, you can also advance across a gigantic open field against enemies in good cover and still take zero casualties as long as you have fire superiority.
Sometimes I think players get too focused on sticking to cover as much as possible. I see people do it in videos and I often catch myself doing it. I become obsessed with cramming all my troops into what little cover is available and then I end up hurting myself because not all of my troops can form a good firing line from inside the cover. My troops become too constricted when I try to only follow what cover is available. And then it gets even worse when an enemy artillery barrage lands on all my troops bunched up in the cover. If I just move some of the troops out into the open and spread them out a bit more, I can get more angles of fire going against the enemy positions, more firepower can get focused outward, and things get easier. Even troops lying prone on open ground can still be hard to hit, especially at a distance.
Units are also the most vulnerable in CM when they're moving. Stationary troops seem to be harder to hit for some reason. It all depends on the situation of course, but I've had success when crossing open fields not by trying to charge across it as quickly as possible, but by taking it slow, stopping frequently (but not for too long), and shooting at everything in sight. CM seems to be a game less about whatever terrain you're in, and more about firepower and angles of fire. It's about getting more of your guns to bear against the enemy than they can, so that the moment they open fire they will get blasted instantly by overwhelming return fire. You wanna think about terrain not in terms of "how open is this?" but more in terms of "can I get a good shot at them from here?" At least that's how I see it.

I have it in the final testing stages now, so I really hope so.

It depends a lot on terrain - both how much tall grass/weeds there are and if you're trying to crawl down a slope facing the enemy, etc. Also the relative experience levels. On this parched Italian hill, there's probably not enough vegetation to be sneaky.
In many cases, it's perfectly possible to crawl into position unseen. But in any case, one should not play WW2 with a modern warfare "spec ops" mindset.

I think that part of the problem comes from traditional army "battle drills". These documents always use scenarios where you have a platoon attacking a single enemy squad. That squad is sat in a Bush and they've seemingly been left all alone like some sort of punishment.
 
Of course a text book fire and manoeuvre approach is easy here, but how often does that scenario occur? 
 
I understand the need for the rank and file to have simple and easy to understand instructions, but is not as easy to find instructional materiel for lieutenants and captains on how to approach attacks to more complex defensive setups. I guess most of that relies upon the same principles being applied with a dollop of common sense.

One piece of the puzzle is to always drop the camera all the way down to pixeltropper eye level and have a look at the terrain. Use the zoom feature and you may find your men can actually see the target building from an action square or two further back than you thought possible from a higher camera angle or there may actuly be a path the assault troops can take that will keep them under cover.
Remember in this game you are the commander of every unit, it is not being a gamey bastooge to look through their eyes.

Whilst on the subject - this is a battalion MG section in the 1943 US TOE for CMFI, as depicted in the above video.


 
Of particular note is that the above section has no radios - neither the section leader, nor the jeeps have them. The only radios in the platoon are with the platoon HQ unit.

That means that this section will have to fight within close range of themselves by necessity, and share information manually - the section HQ (which is one chap) is going to be running around a lot. The jeeps contain additional .30 cal ammunition (1500 rounds), which might be fairly obvious.

 

Quite a bit of that video is about indirect MG fire, which we can't do in CM. The point still holds though.

13:15 is where the "how to get into position" starts, which mostly involves "just rush into position if you don't have cover". The part where the squad leader is picking targets for them is simulated in CM by sharing spotting contacts though, so paying attention to those is important.

Yeah, it's tricky. The scheme that Heirloom_tomato outlines is good, but it's worth breaking this down a little.

Defining the problem:

Setting up an MG takes time, so in an even fight (an MG and an opposing squad rushing up to facing covered positions), the squad will probably win, simply because the MG needs time to set up, and the squad has much greater situational awareness, owing to a greater number of eyes. Once set up, the MMG/HMG should win the eventual firefight, but if it doesn't get the chance to do so because the MG is suppressed, then you're not getting anywhere. That means that you need something to shift things in your favour.

Compounding this, tree cover is ambiguous. Particularly in CMFI, terrain can be sparse and inconsistent, and it can be hard to mask an entire unit. It only takes on chap being spotted to rumble the whole thing.

In the above screenshot it also looks as though the wall is down the slope. That means that the appropriate position for observation is not the facing wall, but instead the hillcrest covered by forest. The alternative is that you'll likely be spotted through tree gaps as you make your way to the downsloped wall. 

In terms of concealing this movement, it's important to play the odds. Slow movement helps, and definitely setting short cover arcs to hold fire. What also helps is using the minimum possible number of troops.


So, in this scenario I think what I would do is scout with the platoon leader, which would hold fire. The mortars deploy behind the ridgeline, within shouting distance of the HQ's intended position on the ridgeline (four action spots is reasonable). I'm going to assume that you have zero smoke available - there's not much smoke for US forces anyway, and there are too many factors that can come into play - wind direction, weather, etc.

The HQ (and only the HQ) Slow-moves to the ridgeline, to a spot with LOS to the house. Since you'll be moving a small number of troops, slowly and through woods, holding fire, you'll have the maximum chance of doing this undetected. If you can't, then a mass-assault may be the only way - rushing up and overwhelming them with fire. That's not the first plan though.

After gaining LOS on the target (which we're assuming you know is occupied already - if not then this HQ is going to be observing for a number of turns, since you won't have many eyes to spot with. This is where good C2 links and multiple scouts with radios become useful), then you do two things - start planning your mortar fire mission, and start planning your MG placement. When the HQ has spotting contacts, you can move up the MGs (still behind the ridgeline) to collect these using horizontal C2. That'll be important in a minute. The same applies for any rifle squads that are joining this base of fire, but the deployment of the MGs need the most thought.

When the fire mission has been plotted and starts landing, now is the time to rush forward the MGs. Mortar rounds suppressing the enemy give your MGs the time to set up in your pre-planned positions, and the shared spotting contacts allow them to find the targets most effectively. You're stacking the deck in your favour. Once the MGs are deployed then you should have sufficient firepower to allow the supporting rifle squads to move up, and eventually to give the manoeuvre elements freedom to move.

MGs are important in the attack as well as the defence, but they do require some more thought. 

Training film, with some useful things, including a depiction of this kind of leader recon at the six-ish minute mark.
 

From the same book you link to:
"Units without mutual support are doomed. Mutually supported units protect each other from being fixed or assaulted."
Remember to compartmentalize the battlespace - find the places that can be isolated from the rest of the battle, due to woods, buildings, hills, smoke, fog, etc. and then focus on those. As you found, it's no good being able to suppress three buildings in front of you, if your assault team can take fire from other positions on the sides as they cross the open ground.

Not wishing to lower the tone, but am I really the only one to have had a really disturbing and inappropriate mental image in reponse to this line...

This is not something i usually do but i wounder if it would be useful (vs the AI) to place some smoke at the intendent overwatch location just prior to making the final move into position...
Allowing the team to be stationary and set-up as the smoke clears (hopefully 😎)