I feel a twinge upset we've got these three other fist fighters...ESPECIALLY SINCE KALIB USES A SPEAR!
Ahem. Anyway, Delta'd be a close range, rush-down type of character who, for balance, can dish out big damage, but has low health. A bit like Akuma I suppose. Normals would be your punches and kicks befitting a martial artist of his ability but the specials... They'd be interesting.
See, with my gimmick of melding the Persona and the user into almost the same thing, he'd have specials that change up his normals. Using Ramses to cast Ziodyne on himself would just be a damage increase, while diamond dust might grant access to other specials. The beauty of it is that he'll eventually have access to all the elements I think, so that's at least 8 mode changes essentially.
For a finisher, he'd have a raging demon esque combo, complete with him and Ramses posing for the victory screen (or not depending on health obviously).