I made a similar suggestion some time ago and ATM the AI just behaves stupid where it should be frightened. If you are a small lord, just one province under your rule, do you join a rebellion if there is a 15k strong Knigh-Retinue in your lands, ready to crush your laughable castle in just a few days?
Do you join rebellion as a craven man if another treacherous duke has been killed? And after his son started another rebellion his whole family was send to the execution site and their house did extinct? You would not like this king that has the strenght to crush every rebellion the last 20 years but at least you would think twice about organizing a rebellion by yourself.
Also I would like different ways to deal with treacherous scum. I mean, cmon. As a King our right to rule was given by !!!GOD!!! we are the legitimate ruler of this land by the lords law! If someone revolts because he does not like to pay his taxes he is a sinner against the world order, the word of the holy father himself! (At least if we make it look like this^^) So I would like to see some ways to deal with this dukes based upon the crown authority. We can revoke titles under certain circumstances. But with the absolute authority, where our status as gods vassal is stronger than ever before, are we not allowed to simply execute this scum? Perhaps not their whole family, but at least this pesky duke. Or we just could banish them all into oblivion.
And yes, I think there should be another opinion "indicator". Call it fear, call it respect but at least introduce it. Someone would hate me, that regularly happened on the court, but that does not turn a honorable duke that follows the laws of his ancestors into a traitor. Its just ridiculous that just because we do not like each other a war is just a matter of time. On the other side, just because someone likes me this does not prevet him from achieving his own goals. And a craven guy is very unlikly to start war with a strong ruler. Perhaps the "respect" rating can receive a +30 modifier for any won faction war in the last 10 years? But if you have lost this would be -30 and even the weaklings would try to break loose. So the respect can work both ways. On the one hand it can save a large empire as long as a strong ruler is on the throne. But when there is a weak one, that looses ground, a chain of "events" breaks loose because when the stronger ones could get their independence the weaker ones are more likly to try that too. And this might lead to an empire wide collapse.
But at the moment all we can do as the ruler of a large empire is to delete the events for civil wars, bribe our vassals to make them stronger, aim for positive traits and be the overall kind ruler. Hell, even a emperor of mine got the "the Kind" surname in his first 10 years of reign... boring 10 years... but then he became the conqueror of the HRE... thats about his kindness... and now I play with a glorious line of cruel sometimes-bastards that send their vassals to prison and appoint their retinue leaders as dukes and lord. Why? Because even the most laughable idiot that holds a country with a opinion of around 20-40 will join a faction... its just a matter of time... so my emperors trust nobody and regularly perform some rampage-madness-roudhouse-kicks every 20 years to prepare the empire for the succession.