Linked Clans/ Feeder Clans
I have always thought that it would be cool if we could link our feeder clans to our main one, and even perhaps have the clans titled as mother clan, and feeder clans. The main addition would be a link to the feeder clans near the clan description to help players become more aware of their brother and sister clans.
Most, if not all, decently ranked clans have at least two other clans associated with themselves where they can send prospect players to farm.
Another feature that that would be extremely, extremely handy would be an easy way to transfer players from clan to clan (perhaps elders, or if you were were to add more clan ranks, players one rank above elder could send transfer requests to players that when accepted would send that player to one of the clans linked associates.
last but not least, donation counts would transfer over to all linked clans.
another possible clan feature would be if you added "joined" dates under peoples profile to mark how long they've been with their clan.