15th Character Workaround

While the 15th Man project works on, I was pondering some manner of workaround to get a 15th party member that is at least mostly workable using what is already in FF6.

Say I do a replica of the Ghost recruitment on the Phantom Train, with General Leo. You revive Leo via a new event and he appears aboard the Falcon, talk to him with an empty slot in the party and he'll join your party like the Ghost. Just like normal guests, the player will be able to use Leo as a playable character but cannot equip him Espers, teach him magic, or change his equipment (so he wouldn't be seen on shop menus anyway, nor the menu equipment screens note what he can equip). If the player changes their party Leo will not be in the party select screen but will reappear aboard the Falcon to be spoken to again.

Would this be do-able and how functional would Leo be?