I'd like to see more done with religion for sure. I think that all religions should have some sort of effect throughout your empire. But unstead of Firaxis making those decisions, which would be political dynamite for them, the effects would be chosen within the game by either the AI or the player. There could be 7 positive effects and 7 negative ones, all with traits/flavours attached in the backround. So each civ who founded a religion would pick aspects that corresponded to their own traits. The human player of course would get to choose what they wanted.