Vaan as main character is like Watson telling Holmes's story. I always believe that Basch and Noah are the strongest character (I mean strong in conceptual) and I guess that's why the logo is Gabbranth with blood stained on his left. in the end, Basch is Noah, and Noah is Basch, both become an individual named Gabbranth. it's Basch and Noah's story.

But ...

Ashe is the central of all characters around. Vaan and Penelo are her people, Balthier and Fran are from opposing country who knows much about nethicite (something she after), and Basch is her bodyguard.

But, I personally prefers Balthier. as Vaan, he's the Watson in Holmes's story with more character depth.