Well, you can assume a modern rendering engine. Nice terrain, volumetric smoke and clouds, visual effects, all the toys on that side of it.
I'm not worried about the flight model at all, I have written them before.
It's a lot of work though.
I would want a single player campaign to get people into the game. Starting as a raw recruit turning up at flight school in England/Germany/Russia/USA and graduating to flight orientation school.
In flight orientation school you get to specialise. Fighters, Fighter Bombers, Heavy Bombers etc. You get to fly them and pick one to specialise in. (I know this isn't realistic, but it would work better for the game).
After that a few weeks of Aircraft Orientation School. You fly your selected aircraft in a set of training exercises. Then off to the front.
I would have to really on you guys for all the content for that, maps, missions, aircraft, you name it.
Multiplayer is always an issue, but I can write better network code than COD so I'm not too worried.
I would have to write a load of tools for you, but again it's just work. Find the time. Write the code.
Let's all have a think about it.