What Is The Most Likely Class To Be Added Next?

[Berteaux_Braumegain]

Some kind of shape-shifting job, they have made multiple references to shape-shifting for combat during SHB so far.

Morpher? That was a Nu Nou Job in Tactics Advance.

Chemist for healer.

This seems like the likeliest option I can think of, though. And if the next expansion is Garlemald, I could see it being a Garlean inspired Job.