I guess a two-stance mode that is inherently different for everyone would be interesting as a baseline thing?

AST could add (weak) regens or (weak) shields to ~all their skills. To not lead to the same balance issues as before the actual effect would need to be tiiiiny though, in return the base healing is buffed I guess?
SCH gets Selene back, obvs. Now since ~all about fairies changed she needs a new role, she nukes stuff and fairy link is now a damaging effect!
SGE essentially gets Philosophia baked in, Kardia swaps between being on one target, or spreading the healing evenly to targets around the sage. Not more healing though, so like with AST, really weak effect overall.
WHM gets their beloved Cleric Stance back, but different? It augments all effects but burns extra mana for every spell cast, and its a flat amount so it's "costliest" on nukes and stuff that are usually cheap, and worst on otherwise free effects (yes, it affects everything).