2) Is there any way to change the game and let units have >2 special abilities?
You can create preset units with as many special abilites as you want by altering the alpha.txt. This idea is discussed at length in the Creation forum .
1. SMAC 2 could be great, and I think it would be fun, but they would really have to expand on it (I don't see why you can't have a multi-planet game, now THAT would be cool)
2. I don't think so. If you could, it would be extremely expensive. Look at the cost of something like a clean cloaked singularity gravship or something like that. It's a bundle with 2!
3. Go look at the official site or something. It should be there.