I like the idea of an Epic game, I agree that Marathon might be too much, when it comes to figuring out orders for military units in wartime, or settlement options early game. That said it is possible for a D.P. to end a session early when a significant event has occurred and he feels that more orders are necessary. However we wouldn't want that to happen too frequently, playing a Marathon game 5 turns at a time would drive a few of us off the deep end.
I'd prefer a random civ with a selected leader. I think that allows us the fun of something unexpected, while not allowing us to be really screwed over from the start. Any civ is playable, if a decent leader is selected.