There is always a way, just check my dissidia custom DLC's lool
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I'm afraid model swapping and configuring to an already established cmd set is quite different from this. I mean with the right knowledge Kurasame, Tonberry, and the "????" character could be used but GILGAMESH is a whole different ballgame. His preset commands are not his but Ifrit's. At least with whoever who made the CWcheats for them. I don't think he got a established command set and I'm no programmer. So yeah. There's also a curious instance when one character does not have their own profile but is mentioned in GILGAMESH'S as a blurb at the end. Makes it seem like GILGAMESH would have been a character under your control. Which means the Agito Tower would need his help since this character in question mentions that you need to be a Type-A L'cie to go through it. A Type-B L'cie wouldn't cut it. Or you could try your luck. Course again there is a bunch of unused stuff. Models and whatnot.
But yes your work with Dissidia is quite impressive.