I think it will be Gauis, and him looking like an FF12 Judge might be the only factor not to consider him.

As for Yshtola representing FF14, I think they went to look for a good female character, so as to increase the females in the roster, and that it could be possibly that they already know she will stay alive all the way to the very final MSQ, a characteristic present in all representatives (yeah, even Tidus fit that).

Though SE could have just used the deplander to represent 14, that way everyone of us could have felt being a part of Dissidia lol.