They would be like the Super Friends!

Fighter would be Superman (cuz hes the oldest)
Firion would be Hawkman
OnionKid would be Gleek (the Wonder Twins' monkey)
Cecil would be Batman
Bartz would be Jayna of the wonder twins
Locke would be Samurai
Cloud would be Aquaman
Squall would be Wonder Woman
Zidane would be Zan of the wonder twins
Tidus would be Robin, because of his uselessness