I could live with this, though I guess someone should make a chemist design thread to discuss it in detail. I would have the item in the ammo slot act as a stat stick to increase the effect of your "potions".
The target limit on Chain Heal is actually pretty notable in a 10/25-man raid. The balance at least when compared to WoW's WHM equivalent (priests) was that priest's AoE heal was heavier on the mana cost and I believe Chain Heal hits could individually crit on each target hit. The fact the spell could prioritize targets based on amount of HP also meant it would hit whoever needed it most, which is a pretty big gain in encounters where you're already keeping an eye on debuffs, mechanics, movement and environmental hazards.
Considering XIV's cures scale with MND for WHM, I don't see why "potions" for CHM wouldn't scale with a base stat that makes sense for them.And passive abilities 'potion potency +10%' or on gear etc etc... just doesn't seem fun.
I was thinking more along the lines of them having a single-target heal called "Alchemist's Potion" (animation would be the chemist pulling out a potion and throwing it at the target ally, the flask shattering and then a swirly heal effect), a ground/zone target heal called "Homebrewed Hi-Potion" (again, the CHM pulling out a flask, throwing it at the area selected by the player, and the ground showing colored vapor for the duration of the effect), a status removal ability called "Remedy Dart" (CHM loads a flask into their pistol/rifle, shooting it at the target player then swirly heal effect).