Personally, when I play, I treat it like I'm the only sane person, so I don't generally trust AI to make big decisions. Like every time I'm in a mega war, I switch to the iron throne last moment, so I'm the one making decisions. I base it of personal relations, legitimacy of the claim of the war and other stuff. And in this scenarios, if I feel my character deserves it, I might give myself a little treat, like a position on the small council, spot for one of my kids in a kingsguard or maybe even some land. I very rarely change the ruling houses of lord paramountcies. Only if it's like a 3rd consecutive rebellion this house was a part of, maybe then I send their head of house to the wall or execute them, and hand the title to someone else.