I agree with Fynn, Ashe is the main protagonist of XII, Vaan is simply the POV character. Also, if you want some good development for Vaan and Penelo, check out Tactics A2. That game may have screwed up the main plot but it actually gave the returning XII characters some justice after the trout show that was Revenant Wings. Vaan is trying hard to be like Balthier and bumbling through it while Penelo acts like a straight laced version of Fran who has to smack Vaan over the head. It's pretty amusing.

I'll get back to this thread later, I have too many characters to sort through first.