One of my favorite things about this game is the ability to create a sophisticated race with its own history and culture and ethics. But, we always start with the races being... new.
It it would breathe life into the galaxy to be able to start a game where there's already a large and powerful race, or two. I'd love to start and lead a rebellion. or to be an ancient race returning to this world with their technology and power.
it won't be balanced for multiplayer, but for single player people like me would love to be able to set how many planets a speacies starts with, or tech level with random techs given. Stuff like that.