I think having a co-leader option in a faction would be a good idea. The co-leader would have the same powers as the leader (except maybe not be able to kick the leader.) Having a co-leader would come in handy when the leader is busy and not able to attend to his duties.
Obviously, when choosing a co-leader, one would have to be careful so the co-leader does not go rogue, but chances of that I believe are slim. Anyway, what are your thoughts of having a faction co-leader?