I also want alchemist healer which use potion as healing method, but i also suggest that their healing style will focus to regen, i know that for now WHM has the most powerful regen spells out of all 3 healer, but that not enough

let see what if alchemist has stackable regen as a main heal spell, you cast that spell like 4 or 5 time on target, each time will give them a buff stack and increase healing power, you can also has some instance heal spell but they are only for emergency situation, that healer will need sometime for their healing to wind up first but once it set, you can have more time to DPS, even better if their DPS focus on DOT spell, which will fit nicely with their healing style