That’s a neat setting. Do you have a particular situation in the setting in mind for players or are you just going to bounce ideas off them (and they off you) until you’ve settled on something? I’d advise at least starting out with the specifics: playing as rebels, playing as counter-rebels, court intrigue or daring violence, whatever. You don’t have to stick with it, but having a “first bid” on the table gives players something to mull over and embrace, modify, or reject.
Be sure the players understand that Elves and Men don’t balance even more than BW in general doesn’t balance. Maybe consider allowing Men more lifepaths. You know your group and how it will handle this sort of thing better.