Chemist/Apothecary is my personal wish, but I think FFXIV mechanically has itself cornered regarding how it can build healers. I do like the idea of a lifeblood gauge, but being reliant on a second, highly limited resource could make many instances pure agony if a tone of burst healing is required. This is something SCH struggled with for a while.

My general lack of imagination and fear of unbalanced mechanics have me just thinking our fourth healer would best be reskinned WHM with DOT heavy DPS. Chemist, I always thought, would use Ninja inspired command sequences to “mix” certain concoctions, and borrow from AST’s ability to store card buffs to toss those mixes in sudden emergencies. Weapon’s a handgun. Mana usage in non-existent, but cast times remain as the player is “mixing” potions.