should be possible. All needed hooks are already in the plugin. Just store a tuple of tribeID and time for each player and check this. However i don't need it for my server and currently i am work at other stuff. So don't expect this to happen soon....Suggestion, Make so if a player leave one tribe (XXX) and then joins tribe (YYY). He can't go back for tribe (XXX) in a few days. Example: Player left tribe (XXX) to join another tribe for a raid, when they finish the raid they will want to go back to their original tribe. Dunno if it's possible.
It will be great for servers that don't allow alliances. Or maybe just a Database marker, if player left tribe (XXX) then joined this tribe again it counts how many times he left the tribe and got back.