I thought what if you were able to have rivals in the game? Such as the folks that destroyed your homeworld in the first place, but for some reason they wanted to finish you off so they sometimes try to invade your new homeworld every now and then. Maybe they would get increasingly difficult as you progress through the game as well. I guess it would be kinda like the rivals in the pokemon series.
Kinda sounds like Spore, getting to the center of the universe and the Grox. ( damned Grox. >_< ) But yeah, this kinda sounds like a good idea, maybe not a " rival " but more of like, a conquest of revenge?
