I've been trying to get a female ruler dinasty going, but it seems that for Absolute Cognatic succession you need to be of Basque culture. Damnit.
Note to self: get a Basque mentor for the young heir.
Elective works, but I can't grant land to women, which sucks. There were many landed women in the history.
It takes working to make an Absolute Cognatic succession... and a bit of assassination/political management...
I don't remember the requirements right now, but I think...
1. Being of a heretic religion is required, that was such a pain..... especially when starting it out and you have cruddy rulers... people hate you. When you get to duchy size or something later on, you need to find yourself a kingdom to attach yourself to, for their protection, else bigger fish will declare holy war upon you.
2. Your duchy liege will be a pain in the arse, as a single county... I was spammed with "Change your religion back to Catholic." Its really doesn't help relations. Might be because my liege was Zealous, I should check.
3. Your kingdom liege, who is most likely catholic and think you a heretic, will get it into his head to demand counties from you. The bastard. Might have to do with personalities though, I should check that...
So pick a weak king that won't steamroll you if you intend to fight back, for at least white peace. (While you are fighting for the right to keep your county, others will get the idea to declare holy war on you... that is when you ask for white peace. When it is accepted, all holy wars on you will stop.
4. Since you have heretics, your liege and if they have a liege too... they will ALL likely be sending their priests down on your province, doing the inquisition thing or whatever it is. Random courtiers you have converted, will convert back. If you managed to turn the county of your religion, expect it to be turned back right quick. Lots of RNG luck to spread your heresy... or at least keep it manageable.
5. Getting your female ruler to have one of those fancy titles. I only know how to get 2 of em... The one for prestige and the one for piety. It really helps to have some decent traits... it helps a lot.
My latest success was on the 4th ruler in the line of succession, 1000 prestige to become 'The Great'.... it took about 40 years of her life to get up there.