If not that, then I'd still like to see deposed monarchs and their descendants more frequently have their claims pressed to restore them to their rightful thrones. Maybe something like when someone asks you for a title and you promise them one, they could ask you to restore them to their throne, and if you fail to deliver, then they move on to somebody else's court to try it with them.
As it is now, they just seem to marry into other families and die out without a fight.
Well, I know it isn't the same as what you are asking for but In my last two games I have dethroned the Capetians and I see quite a few factions created to return the last king or an unlanded or lower level Capetian to the throne. I have also seen factions to place my relatives with weak claims to the throne that I married off into other courts come up. So the option is kind of there although I would prefer to see a Tostig Godwinson type event myself
Honestly TS, the game kind of varies when it comes to whether Christianity or Islam blob all over the map. People used to complain frequently about the Fatimids or the Iberian Muslims wiping out France and the ERE and while I did see this a fair bit in 1.06 it seems to be a lot less common in the recent patches for whatever reason. I think the tipping point in your game was both hordes converting to Chrisitanity which is something I don't think I have ever seen. If it happened early on, that is a lot of fire power directed at the middle-east. Castille has become quite the little crusader in the last couple patches. Still it does seem that certain actions have an intense snowball effect in the game which can lead to some amusing results.