Alchemist make potions, so i don't see why they'd add chemist that toss potions at people - they can just buy potions and use them - it's kind of weird theme to have "toss" as job description.
If it use guns, it just sounds like a Machinist as a healer - like, instead of auto crossbow, you shoot healing syringes at your party? The whole thing just sounds so weird to me.
Sage with ion cannon sound more interesting as far as science barrier-healer goes though.
Or Ironworks created a time-machine, so you could have a science based time manipulator to reverse damage, and cause damage to enemies - i don't see the the point in potions or such.

Well, i think the only reason they brought it up, is because a lot of ppl have requested it, and still do, but if they haven't yet in how many years? Then the concept is still weird to them too. I don't think it's just "writing themselves in a corner" it's just a weird theme. It feels like grasping at straws, to try making it work.

but if they manage to do something interesting with it, then by all means.
I thought Dancer was awkward too, but they ended up adding it, and it's still awkward i hope they revamp it like they did with MCH.