I agree with all of you and here is some of my humble thoughts:
Historical Scenario design is impossible other then the terrain of the map and including elements of the TOE. However, You can provide historical facts in the Briefings.
Making your scenario fun and challanging is the important step in design. Here is where the challenge really begins.... Was the secenario designed for XXX Vs. AI, or for head to head play. Do you slant the TOE or follow it to make the challenge in the above situations more difficult. I tend to follow the difficult and challenging mode when designing the scenario and concentrate on terrain features. Most of my time is spent just tweaking terrain, then spent on type of play to make it difficult for either side to win. If it is set up for AI I make it very challenging for the human side to win.
Size of scenario varies, I would think most of my scenarios lean towards medium to Huge. For the new players they need to be warned what each size means. If it is an operation I always suggest not to play more than two battles in a day(for the time issue). Besides as in any HUGE map it takes up to Four or Five times longer to create as a designer and should probaly take that long to play too.
Most of my succesful scenarios that have been downloaded have been the 25 to 30 turn scenarios, and I belive most of the Scenarios on the CD should be the same. I believe the split should be about 80% 25 to 30 turns, 5% short and tiny, 5% 30+ Large and Huge, and 10% operations.
I also believe that as usual the scenarios should be playtested by people from all levels of CM experience, from the raw Green Player, to the true hard core wargammer, and if is designed for true head to head format by all means TCP/IP-PBEM players.
Wild Bill as a former playtester for you, i believe that your team will be as thorough as need be and scenarios will be fun, and a good mix of scenarios will be forth coming that will satisfy current CM owners as well as the new players CMBB will grab out there in the world.
Michael "Gonzo" Gonzalez
P.S. I would be happy to playtest for you any time.