@Meneth: I figured out a possible reason why there are so few claimant wars in the Byzantine Empire:
there aren't that many claimants in the first place. At least for the 1066 start, that is. Browsing very, very quickly through the Greek characters' history file, I noticed most of the claims on the Byzantine Empire came only
after 1066 (the earliest I found would appear in 1068). That would explain why the Byzantine Empire only has about 3 or so claimants at game start - compare this to England which has three to four times that many and will as a result inevitably go through several claimant civil wars (at least before the new version of PB). Thus, in the case of the Byzanitne Empire, I would assume (though I can't confirm, given that I don't really know anything about how factions are programmed to work) that the rather arbitrary AI will not choose to join claimant wars as often simply because there are so few claimants.
In my mod in development, I'm trying to come up with two methods to fix this, two you might want to consider.
The first would be to somehow make it possible for dukes in the Byzantine Empire to claim the throne through some sort of event (as fawr did so in his mod) or some decision or the like (so a duke with, say, 1000 prestige or something can lay claim to the throne). The intended result is for more claimant wars. While I'll probably be trying something like this in my mod, it might not suit PB since as a new addition it might cause further balance issues and unpredictable results.
The second, easier, and less intrusive solution (and the one I think would suit PB more) would be to simply have more claimants to the Byzantine Empire at game start. For instance, all or some relatives of Isaac I Komnenos, particularly Alexios Komnenos (since he's the one that actually got the throne and lived, and since I have a soft spot for him), can be given (weak?) claims to the Empire (or strong, if you want - I don't know how much of a balance issue that would cause). Other Byzantine characters who could have claims to the throne would be Romanos IV Diogenes and Nikephoros III Botaneiates (since although they weren't directly related to any Emperors or Empresses they still got the throne eventually), as well as any other characters related to Emperors already dead by 1066. In terms of balance I think this wouldn't really effect things too bad, and it would also help in historical plausibility - ideally I am assuming this would increase the number of claimant wars in the Byzantine Empire, and would also mimic the historical dynastic changes a bit better at the 1066 start (rather than having the Doukas sit on the throne forever). While the Byzantine Empire wasn't always in civil war over claims to the throne throughout its history, it's less historically plausible that there aren't any people trying to seize the throne at all save for some random claimant faction for some random female courtier from nowhere nobody ever joins in my games.
Amusingly enough, the first plot against my Byzantine Emperor was to institute Elective Succession.
It wasn't the first plot against the Byzantine Emperor in my game, but it was certainly the first open civil war.
