I agree with Blam about the database. If more scripts came packaged in with the game, or were more easily found and downloaded (as opposed to digging through the scripts board and hoping to find a good one) then it would let more people know about scripts and what they are capable of. The more people who know, the more they get made, more new ideas, etc...

And yes, the replay fix would be good also, and multiplayer capabilities seems like a no brainer as a good idea.