A well- discussed topic, both before and after HF.
It´s a delicate problem. Even more so now, after HF. I have still seen Catholicism collapasing into oblivion before year 780. I have also seen Umayyad in the same situation, where Iberia is carpet of independent Catholic counts and dukes, all of them provincial revolts of different types.
The middleway, a Status que or slow Catholic reconqueista, seems very rare.
so.. What can be done?
Well. A list of small things to pick from
1. Improve Charlies diploskill slightly or maybe give a friendly vassal with a high diploskill to give him the ability to handle his vassals.
2. rescript to Charlemagne historical events to not take the decision to invade Saxony when having high threat.
3. Make Charlies main focus after uniting Karling realms be defence and creation of HRE/ Francia.
4. Let the game start with a countymodifier to provinces bordering Catholic and Umayyad(both sides) that lowers enemy supply. And give these provinces the first level of fortifications instead of a free stable.
5. Let Karloman´s primary title be a titular kingdom, that is also deleted when Karloman is murdered in the event. Inheriting this title does not only make Charles far over demesme - limit but also makes the de-jure vassals of the secondary kingdom(s) hate him.
6. Talking about demesne level... Let´s have some more ducal vassaltitles clreated at start..? I find myself spening all my gold on creating vassaltitles to keep under demesne- limit.
7. A cheap merc that´s available exclusively to Charlie during his wars? "Carolinguan Guard"? He wont be able to steamroll the map anyway because of peaces and/or threat%.
....