I've been toying with something like this too! I do think one obstacle is what the ingredients are/where they come from/if they have a price and what happens if you're broke or unable to obtain more.

If you have a nebulous "kit" of some sort as your weapon/gear, you could have a "restock" action when you run out similar to a mana or stamina meter. If the item you use is say, a giant syringe, you could have a "refill" action. Basically just suspend disbelief with hammerspace.

Frankly it might also be fun because then you get an option to do either medications or poisons. Heal party members, give buffs, etc. or inflict damage and status ailments on enemies. Possibly initial damage inflicted could be low, but then when you stack loads of potentially crippling status ailments on top you could potentially go full-morbol on your enemies.

Might also be interesting depending on whether it is close-range requirement, and if it added a healer that wasn't using magic.

I've said before on the site, but I also still think there's room for a caster who manipulates aether in the body either in beneficial or harmful ways and could inflict crippling status ailments in similar ways. I basically think that healer/status ailment combo is something that would fit in great whether it's a mundane or arcane approach. I know dancer and geomancer are things people are clamoring for, but I would LOVE something a bit darker or otherwise more unusual personally.