well, I started a game in the early start date, and I have met one very hard to kill king of west france...
I was originally a vassal of lotharingia, even managed to get a relative on the throne, then switch to elective. my vassals refused to vote for the king, but I didn't really mind. at some point, they even preferred to vote for a possessed guy, which made me turn cathar and convert all my vassals ( a sizeable portion of lotharingia.). this of course was not much liked, so I had to declare independence. the war was quite easy, because I was quite powerful, and much richer. Problem is, it seems that lotharingia was now ruled by a queen. which decided to marry the king of west france (not matrilinearly)! since she was the second wife, at the beginning I am displeased but not worried: the 2 kingdoms will not combine.
but I was wrong... stuff happened, and now king of west francia is heir to the kingdoms of lotharingia and burgundy ( both ruled by my relative). such a neighbor would be able to ruthlessly crush me, since I am heretic. so I resort to assassination. after many costly attempts, I kill the king. and his son . and his son's brother. but eventually I fail to prevent the merge. However, the kingdom is destabilized enough to not be concerned with me, and so I survived the 2 crusades against me.
I still try to destabilize it a bit more, and at some point it seems I succeed. there are rebellions firing for francia and burgundy, and they are winning. Perfect! I spend some time dealing with a crusade sent against me, and the usual invasion from bavaria and frisia , then I see that my enemy has lost kingdom of france to his vassal.
AND THEN HE INHERITED ITALY!
italy, which is much stronger than france.
I guess this is not going to be easy.
on the plus side, catholicism is suffering greatly. heresies are all over the place. and hadn't west francia formed that power block, the old lothringia would be mostly cathar.waldesianshas a couple of kingdoms in spain, and there are fraticelli here and there. however, templars were getting stronger. at some point, they had half of england, and parts of bavaria. this game is turning to be quite unusual...
edit: here is the religious map