After rebellion, rebel leader or old ruler, whoever wins, should have option of dismissing dukes from their seats, in some limited period of time (few turns at most, or even immediately).
That way rebellion would regain some of its strength which seems to be lacking these days. Currently, dukes, and often many lords, simply stay neutral if they are not completely dedicated to cause (which is rare, as dukes are mostly dedicated to retaining their seats only).
Such neutrality is especially artificial if lords clearly have their side chosen, but still simply avoid all risk for themselves. They can even publicly support one side, deal with funding, deal with militia in capital (I think), while still remaining neutral, and if their side loses after everything, their feud is still intact.
Bloody rebellion is ultimate attempt to derange complete realm tradition and feudal hierarchy by reclaiming it, and should therefore have its real powers. Only those who really do not care for any of rebellion parties should remain neutral, hoping that such neutrality will be recognized by any of parties, afterwards.
Of course, dukes should be disallowed to secede of change allegiance for that short period of time after rebellion is finished, but they should be able to secede/change allegiance during the course of rebellion.
