yeah. or maybe his current body that he'd be in could be stolen, like ainley's master was, to prolong his life and that's taking it's toll a bit too probably. since if he's been around for a thousand or a couple of thousand years, that'd probably not help
but yeah, maybe he's trapped in some sort of prison or something? then there can be some arguments with jack and john with the doctor when the doctor tries to break him out.