I noticed this thread and I would also be interested in playing. I like the open creation workings of Pathfinder but, like yourself, I have not played Pathfinder very much while I have played a lot of 3.5. So I would be happy to play either version of your game. With the Pathfinder version I would modify the basic template to be a variant vampire, for example one that can walk in the daylight but instead of feeding on blood would need to drain the soul of magic users like an oriental vampire. With the monster campaign I am not sure what I would be yet but probably a spell caster of some sort, probably mixed with a construct or undead type of monster.