At the moment SE seems to have decided to walk away from their design philosophy that healers should do damage during their downtime, despite the fact that this is how it's been since the game began. To that end I'd like to see healers take more support responsibilities outside the health pool. Casting buffs and other status effects when healing isn't needed. Gods know that Final Fantasy has a near limitless amount of ideas to pull from.

Hells maybe we bring TP back and make MP something people have to manage. Maybe the healers could be responsible for not just keeping the health pools up but also MP and TP. What about aggro reducing abilities as well? Make threat something that could actually be a problem if healers aren't casting threat reduction abilities.