I honestly don't know how that would work with the idea of trying to concentrate nobles in a smaller number of closer realms, but I love the idea and think it would be awesome.
It goes completely against it, but with the possibility of holding land (however loosely) that you don't need to actually assign Lords and Knights to, it changes the dynamic quite a bit.
I'm hesitant to attempt to apply any particular social/gameplay pressures on top of such a change until we've seen how things start to settle out.
