It's been done for FS2 already, surely it shouldn't take much effort.
Never make an estimate like this when you have no experience with what is involved.
I could see if I could do it, even. It isn't much more than adding more player starts and making sure some missions don't do things explicitly for Alpha 1 I guess.
That would be good. But it
is much more than what you said -- it also requires rebalancing, which is a major task. For an example, going the other way around, from multiplayer Templar (which was designed for co-op) to single-player Templar, requires significant changes in every mission.