A couple of comments come to mind here. First, I was on the com2 brought up here. That situation was different from what you are suggesting, however at the time the server ended I and several other like minded veteran players brought up the need to prevent a WW holder from defecting, especially late in end game. This has not been done, nor as far as I know, has any discussion among devs taken place which might lead to any action. I still say a WW should be a team holding and no holder should be allowed to switch alliances taking the WW with him/her.
Secondly, on the subject of "merging" alliances, although it is done differently in TK, it has always been a part of the game. Players who support an alliance faithfully and with dedication deserve to be recognized as part of the team when a WW is completed. We often added players to the alliance who had fought along with us and supported us, no matter which alliance tag they carried during the server - even if it meant booting less deserving players. The principle is the same here.
As to leadership, no one who has not been in leadership can understand what a burden it is (if done right). It is quite often the exact opposite of fun, and it is very seldom that one is appreciated for even the best leadership qualities. I cannot blame anyone who sees a chance to hand over the reins to another capable leader for doing so - and I feel certain that no one else with leadership experience in this game can blame them either.