as I've said many times before, if there are optional/cost associated skills that are essential for every character, don't make them optional or cost associated. The two from FF:R that come to mind are arms akimbo and damage cap.
Every character needs to have these on at all times. Theyre just a tax for having good characters, which is poor design. (That's not to say the whole game is badly designed, just these two skills being cost-associated instead of unlockable upgrades).
Everyone agrees then that Firion is by far the most important and by extension arguably the best vision in FF resonance right? Arms Akimbo is necessary for pretty much every build. Even better than Terra and her break the limit