Well, not another Persona character, but a mainline SMT character.
The Demi-Fiend of SMTIII: Nocturne.
He's got a plethora of abilities ranging from buffs, debuffs, and healing, ranging all the way to elemental powers, projecting energy blades, a few of his own exclusive abilities.
His overall set could very greatly, but he'd need his most iconic attack, Freikugel. Would want it to be implemented as a very slow to charge and slow to come out, but mostrously powerful and unblockable Thoron-Like beam.
If not him, then maybe Raidou Kuzunoha of the Devil Summoner spinoffs.
For Atlus characters in general, I'd love an Etrian Odyssey character, such as maybe the Highlander, an spear fighter whose powerful abilities consume his own HP, or the Fafnir Knight...who actually has the same gimmick as Joker.