Lessons are never learned when egos get in the way. The most successful MSFT air combat simulation game was CFS2, not the CFS1 or CFS3. CFS2 and the Pacific IL2 are the most successful releases for both companies. What is so hard to understand about that?
The Battle of Britain was a loser for Rowan and he just yielded up the code for it to the community. The Korean war by Rowan was a loser as well and he gave up that code as well.
The best war theatre is the Pacific war, because it had huge variations in aircraft, carrier operations and the scenery was awesome. Gaijin did some things Pacific, but it was just arcade stuff and no one goes for that.
Anyone taking on another European Front will just learn the same things over again. Sadly, if you really consider the Battle of Stalingrad it was a depressing battle, there were limited early war aircraft, the weather and scenery were awful. The battles and engagements were boring as well.
This is free advice, but we all know free advice is worthless and paid for advice rarely heeded. The only thing that seems to matter to the those who produce games, especially air combat games is the devs egotistical imperatives. It seems, all we get in the end is excuses for predictable subsequent failures.