Chemist would make sense as its the most popular choice.

Geomancer would be a slap in the face to both WHM and AST. It would be much better as a caster DPS.

As far as Final Fantasy jobs goes, Chemist is the only healer they haven't added. Like post above said, it was supposed to be in HW and you can see how the card system could work with a similarly mix system.

Who knows what SE will do? I hope it will be something they can meet the fans halfway because going without another healer job while they add more to DPS or tank would definitely be tone-deaf.

While I can understand those wanting to "fix" current healer balance, SE will never be able to because they have shown to be quite stubborn and very dismissive. At this point, I'd rather them try to be experiment with the healers and give us something different and put flavor back in the roles. Both healer and tanks. The homogenization really hurt those roles.