An option to change start eras.

This seems like a good idea.  By the time you get to Eras 5 & 6, the game is almost over (for me at least) and you don't really get a chance to discover and play with the new toys in those Era. Starting at a later Era might give you that opportunity.  As of now, I set the game turns to unlimited and leave at least one unconquered civ alive while I concentrate of researching and building late game stuff.