Starting position is clearly critical in this game. Developing challenging scenarios seems to be a LOT more fun than adding another boring tech. Starting locations, planet quality decisions, simple scripting to add UP and alignment events and starting conditions and postitions would add a lot. Is there a facility for this in the mod kit?
Scenarios could indeed rock in that game. Particularly if they added a few techs restricted to one race, that would allow HUGE modding possibilities (think Civ2 variety of scenarios thanks to that...).
Indeed scenarios that include events with possible triggers etc. would make GC a long time favorite for many years to come. More so then it is currently. I would love to see the ability to edit the diplomacy responses, and possibly add more to them. It seems very limited for producing quality interactive scenarios. This would improve the general game play as well IMHO.