I love the idea of a "Chemist" for the next healer. Probably the name could be Apothecary (APO) so it wouldn't be too close to Alchemist, which we already have.

The lore is also pretty much a given - Alchemists that specialize as combat medics. It could be cool as a healer that appears to be less "magic spells" and more "magic infused items", and also Mix, which is the classical FF Chemist job action, opens up to a lot of interesting possibilities if done right. I mean, NIN also have their job gimmick based around matches and it seems to be pretty successful.