I like the idea machineman9 has. Yeah, really all we need is that to be the engine, and then the talented members here can help it evolve. Simple.
Well that's usually all that an engine is. You have one (or maybe two, if the two need to be 'connected' so that the game can be continuous) of the essential components and then you just build it up because in theory it should all just expand. You demonstrate a tiny aspect working but that shows all the key areas of the game and then you simply make it bigger.
In terms of being optimistic, the hit game Gears of War had a $10M budget, took about 20-30 people and a few years to make. So it is possible to have not a lot of people to help make it, but the engine they used for that game already existed. To us, that would be like taking the MSFS engine and 'upgrading it'. To build an entire engine for the game would take quite a long time.
Personally I'm against the whole opposition thing as a few groups seem to be trying to make their own flight simulators. A merge of ideas as you said, Doug, does seem like a good idea. We have some great developers here... The least they could do, if they wanted to be a part of it, is help voice their views of what they want in a 'new game'. Instead of having lots of small games by dozens of groups, it seems to me like it would be better to have a much larger single game with collective thoughts from everyone else.
I, like a lot of others, like the idea of a new game, but I don't have a huge input on it. I'm not a developer, I am a shoddy programmer (and have since stopped that as it was getting me no where) but I do have my ideas of what I would like to see.