sc2 is worked out perfectly, but that means also more work each turn. Thats why i never play the game online, takes ages between turns. I like it as solo game though. I think more people feel like me and would definitely like to see some kind of upgrade to sc1. Some ideas: insertion of the diplomacy system, extanding the map, more customization options in scenario editor, maybe the possibility of playing with more than 2, some ai tweaks (like trying to make it attack in the best order, not planes first). Like aesopo already told, a lot of pple would like to reward any attempts in this direction.
I still play sc1 with 3 friends in hotseat or online. We all believe sc1 is a better multiplayer game than its offspring.
Greetz