Repliica
The Dream Fighter
Personally, I think they need more secondary characters if they make a sequel. They also should probably include more females, as it is there's only one female on Cosmos' side.
FF1 heroes
Warrior of light (same)
Warrior of light (Red mage)
FF1 villains
Garland
One of the four fiends
FF2 heroes
Firion
Minwu
FF2 villains
Emperor Mateus
Leon
FF3 heroes
Onion Knight (Luneth)
Onion Knight (Refia)
FF3 villains
Cloud of Darkness
Xande
FF4 heroes
Cecil
Rosa
FF4 villains
Golbez
Dr. Lugae (you know it would be awesome! xD)
FF5 heroes
Butz
Galuf
FF5 villains
ExDeath
Gilgamesh
FFVI heroes
Terra
Mog (Just because I want to see a moogle beat people up. )
FFVI villains
Kefka
Ultros.... Well that probably wouldn't work, so I guess Gestahl... >_>
FFVII heroes
Cloud
Tifa
FFVII villains
Sephiroth
Jenova (since it could take the form of others it would definitely be a mimic character)
FFVIII heroes
Squall
Laguna
FFVIII villains
Ultimecia
Seifer
FFIX heroes
Zidane
Freya (I'd say Vivi but he's not the type that could run on walls. xD)
FFIX villains
Kuja
Beatrix (She may have ended up a hero in the end, but in the begining she made an awesome villain)
FFX heroes
Tidus
Auron
FFX villains
Jecht
Seymour
I like this list, Beatrix, Freya, Mog, Tifa and the idea of Jenova being a mimic character all seems so awesome. Plus I like the idea of Laguna being included he was a great character.
I'm surprised Rydia isn't there, I'd like to see that hot headed tree go at it with Terra, magic wise. ^^