I would love to add Zack Fair. Add the evil version of him as a Super Boss who Cloud has to defeat and knock his senses into.

His moveset would definitely be more varied than Cloud's.

Also add Fran as an excellent long range opponent who is only capable of kicking and hitting with the bow up close, with no dedicated mid range moves.

Finally, add Viera, Baanga, and Moogle to the fray.
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Viera would play as either and Elementalist or an Assassin. One of the alt costumes would be Ritz from FFTA
Baanga would be a Monk, with an alt costume as Joseph from FF2
The moogle would of course be played by Montblanc, with Stiltzkin and artemecion alts.