[quote=@Cerberov]
I was thinking of going more for what Spain had in real life: a few of the duchies following absolute primogeniture, including the royal seat, with the majority following cognatic but having less of a problem with female heirs or regents.

Basically: Navarre ended up being the primary power, instead of Castile.

One thing to think of in-setting is Uterine Primogeniture, wherein line of succession is actually followed through female ancestry. Something that was used among the Picts, though they still typically picked kings.

Or you could go with gavelkind, but with the size of the kingdoms, that would get messy very quickly.

Also: Updated my sheet a bit.Still got a good ways to go, but it's taking shape.
[/quote]

Gavelkind destroys kingdoms! Definitely the bane of my existence in Crusader Kings 2. 

Though Uterine sounds a lot like absolute cognatic succession to me (females inherit on the same grounds as men). Sort of.