I ran into my usual problem with playing the AI - I got bored. But I have to say the first mission in the Blue and the Grey was possibly one of my favourite missions. Yes it is winnable - I've done it. I forced the Germans to surrender just as I was organizing my stragglers to push for the final objective.
I agree it was difficult to face a second beach landing after the first one. But you are correct the second one is considerably easier.
What I liked about that first mission *was* the grind. It made me think about those that actually made that landing. Holy Crap! You have to forget your usual find a safe way, find places with cover, make sure everyone is at least not tired and look for the opening. Instead you have to just force your way across and then try to accomplish the mission with what ever depleted and broken men you have left. I'm not saying all scenarios should be like that but we should all take on one of those just to say we have done it. I realized a long time ago in this game that you can force your men to push and push and push. It gets harder and harder as their morale gets worse and they take casualties. This mission was the first time that approach felt like it was legitimate and true to life.
As someone wise has in their sig line "Good wargames make you think"
Yes, do give it a go. Following @JonS 's philosophy and his "during design report" is a great way to get into it. There are a whole bunch of people who are good to listen to as well (sorry I should really name you all but I am afraid I'll forget someone). Just post questions in the maps and mods sub forum and you will get advice. Go for it - more designers is a good thing.