On the other hand, Yoshi-P has said the latest MSQ included hints about the next job, and there was an out-of-place sequence about the girl wanting to be a potion healer. Given the years-long demand for Chemist it seems likely it will at least have influence on the next healer, if it isn't the full job.

That said, I hope it isn't "Chemist" outright.

As we well know, the iconic ability of Chemist was it's ability to Mix consumable items to create a unique effect of greater potency. The last attempt that was made at creating Chemist ended with it being split into AST (with the ability to "Mix" cards) and MCH (with its intended pistol and several chemical attacks).
I would be loathe to see the devs introduce a healer that recycled elements of an existing job, like AST cards or NIN mudras – and the difficulty with creating a unique or balanced Mix system was cited as the reason Chemist failed to see the light of day in the first place.

So the two main options I see are either "release Chemist without Mix" or "rehash of another job in an attempt to recreate Mix", which will leave everyone unsatisfied.

However, as I touched on before, there is a third option: sidestep the issue.
Do what they did with AST, and combine the elements of multiple jobs into something unique. Create something that is Chemist in aesthetic and role, but unique in ability so it doesn't need to be 100% faithful.
Which is another reason why I've been posing Meracydian Witch Doctor, as it not only gives space to compromise with the Battle Healer crowd, but allows the freedom to include the potion-tossing (the only aspect of the job that we know it has) without being limited by Chemist's interpretation.