I would make the chemist mechanic far different than the WHM to make it fun and different.

My idea is I would make it the chemist "brew potions" on the fly in combat. Not like a crafting, but they create potions out of pure aether and only able to hold so many, like 5. So the chemist "casts" potions that builds stacks for use/throw them on people for effects. This makes the chemist a healer/caster that has great burst healing with quick reactions, but has to rebuild his supply after each casting. This also would explain why chemist don't carry or buy potions, they make them on the spot. I would also give the potion have decay, saying they are unstable and disintegrate back into aether if not used. The chemist would also have to manage what potions he/she wants to have ready. With a limit of like 5, you have to think like"Do I want three single heals, one AoE heal, and a heal or two singles, two AoE, and a raise?"

Just an idea I'm throwing out there.