Balthier never seemed the main character type. He's the veteran sidekick. There to show you the way/how to do stuff, but never the lead.
And Ashe was always just the next Yuna in line for me. Always a love interest, but never the main character.
Vaan seems like the perfect follow up to Tidus. They're exactly the same, except Tidus is cooler. And his voice isn't as high. I like that.
I disagree.
Actually they put it like this:
Vaan was the main character at the beginning of the game.
Ashe became a Main character in the middle of the game and till the end of it.
and Balthier started showing himself as a second main character in the end of the game too.