Sorry to interrupt here, yet may I suggest, should you wish to not include certain factions, that you make a "virtual faction", pardon me if there is a correct word for this sort of this, in their place. The concept it that such provinces which would be controlled by a borderline in/out of list faction could have highly powerful rebels in them that, although they may not do any conquering, they are very tough to take over - compensating for their discoordination.
Sorry, cheers!
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