If Yuna was in-game, she would hopefully play off her summoning techniques, not just another straight caster (of which the game has plenty and none of them are underpowered). Since the summons were uniquely hers in FFX, they would make sense to be a part of her playstyle, and I would love to see them implemented.

That being said, Jecht and Seymour were the only villain choices, and Jecht was a much, much better choice than Seymour. Choosing Jecht pretty much assured that they would choose Tidus to pair him with.