When I first heard of rebellions i thought this:
1. Notables relationship becomes more relevant
Explanation:
Because of raiding,war and food shortage they will become more and more unpleasant with the town/castle ruler =>Losing Relationship per day.
At a special degree of disatisfaction they wont be a supporter of the ruling clan and try to revolt. As there are more than one notable, their powerlvl(regular,influental,powerful) will be taken into account if they should revolt(for example 1 powerful notable doesn´t support the ruler anymore and wants a rebellion vs a influental notable who still supports the ruling clan=>rebellion starts). The ruler has options (quests/ governour perks/ war victories/ special lord prisoners) to work against the relationship loss.
2.Plan your own rebellion:
As a Minor Clan you befriend yourself with Notables of a castle/town/village. If your relationship is high enough they will support your clan and you have a new option to ask them to revolt. When the rebellion starts you fight with them against the garrison inside the city and of course become an enemy to the ruler/faction. If you win, you will get the city and a vassal clan(rebellion clan).
But that was only a thought....