The game has already given us quite a few note worthy characters that can't exactly be orgin characters, but would make really neat companions. It'd be awesome to be able to recruit them!
Sazza: Paladin of the Absolute. Only available if you side with the Goblins
Owlbear cub: Basically a scaled down version of its mom. If you can make your Tav a random human that levels up to be able to duke it out with Minotaurs so can the cub!.
Glut: As a Chaotic evil choice itd be cool if we could pass a persuasion check to convince him to journey with us, in order to spread his spores across the land. Obviously a bad idea but it gives you a powerful hechman, Obviously hed have to be rebalenced a bit
The Kuo-Toa Priest: Itd be neat if you could convince him he was following a false God, qnd get him to follow you to find a new one.