Another one that is a bit out there.
How about adding to the "leader" flag some neat kickbacks for leading a group? Nothing major, but maybe the character leading a group gets a 2% bonus to exp or rank? Or some other bonus like +hit roll or maybe we even make it class specific.
A thief as the leader might get a bonus to backstab while a Paladin's god might imbue a greater bonus...I'm thinking modest, but noticeable pluses for leading.
My thought being this may incentivize players to lead more, learn more zones, spice up the zoning grind with a new char leading.