how's that for RP consistency? reeks like powergaming ...
That's things that Pian en Luries did. Which is ruled by a dev. That is, starving the city into revolt and forcing it to secede.
I can't think of anything wrong with simply banning him, if the option is present, but that is likely to just make him secede anyways. Or switch to GDoF.
As for the general thing, it's been done in rebellions since way before I joined up. All of the rebellion guides on the wiki tell you to recruit the general to have him scrap the militia before the rebellion. I've never seen anyone make a fuss about it, so I don't see why it wouldn't be alright in this case. After all, scrapping militia ain't free, and the duke can always recruit them back.
IMO, goes farther for RP consistency than just moving your capital away to a far-off region because the duke won't do anything anymore.