In the event of a lesser house rebelling against their Lord Paramount what does the King do? We know Tywin had to put down the Reyne/Tarbeck rebellion himself, but how far is to far? When does it fall to the king to intervene on behalf of a great house against their own vassals?

As with many political matters in a pre-institutional state, it depends on the King. Aenys, for example, initially pursued a hands-off approach when it came to the Vulture King and other rebels to local authority, whereas Aegon V’s intervention in the Westerlands may well have been motivated both by necessity and his overall agenda of trying to strengthen the central government vs. the great lords.