I say if JM really needs to exit the game due to RL reasons then so be it, AI it up if a sub cant be found (by JM) ASAP. Sounds like he fighting a losing battle anyway so I can't really see how it would unbalance the game. MIght even distract my besiegers for a few turns
In other news, I hate Leprosy almost as much as I hate golem thugs.