it shouldn't really take 2 years to lay down a concept for any game...
Depends on the professional situation of the concept writer.
Perhaps you're trying to encompass too much?
Yes. Thats correct. I TRY to encompass too much. But I recognize those "too-much-features" and take them out of the concept again.
Or is the whole concept just procrastination as Chrill pointed out earlier?
I do not understand the meaning of "concept = procrastination". What do you want to say? That will never be a game, only concept writing and procrastinating the coding forever? What I can tell you: I really would like to start with the coding again. I love it to see results, do the first clicks on the map, move the first vehicles. But I would hate it even more, if the development stops because of unmanageable complexity. P1SIM is a very complex game which wants to be very easy to play at the same time. To achieve these ambitious targets there has to be a detailed concept, answering every single question, forming the base of all coding, helping to stick to the agreed features. Extreme programming will not realize this game.
Since nobody seems to be supporting you I will
Very couragous of you to develop something of this size, by yourself.
I envie your passion and preseverance!
But there are more people supporting the project than you think. Those who question the concept also help by critizing it.