Ive had this idea since the Morrow days. All the races would be the different regions. Thracian, Athenians, Egyptians, Persians etc. Gods and Titans would work like Aedra/Daedra with shrines and quest rewards (Molag Bal just gave you a mace? Poseidon just gave me a Pegasus. Peryite just gave you Spell Breaker? Athena just gave me the Medusa shield (the real Aegis) that turns NPCs into stone)etc.
even native American mythology.
I've had this idea as well. Set right when the colonists (perhaps French Indian war so more Indians have firearms) start to arrive and youd only play as the different Indian tribes.