FFVI: Divergent Paths

How likely would it be to add a few different NPC's to teach the mages their "Ultimate Spell", like for example, how Duncan teaches Sabin Bum Rush, except doing a small sidequest and finding a living Esper to teach Terra "meltdown", finding someone else to teach Celes "Holy" or whatever their respective "ultimate" spells would be? It'd be nice to have some spells locked to specific characters and out of the every greedy reach of the magicite