They've got such a specific aesthetic going for them that I've started wondering if some of Aloalo Island's bosses aren't teasing whatever the new Caster ends up being?
Quaqua, Lala and Loquloqui, specifically, the nature+tech (that's also natural i.e. wood) feels like it could serve as the basis for a Job, especially as WHM has decidedly left that niche behind. I'm not that much of a theorycrafter, but you could probably come up with something by studying their respective mechanics as well.