For SCH, I wouldn't mind a deviation from the Alka + Tonberry Nymian story. Like, the new expansion has Pixies including the primal Titania right? So, what if it happens that Pixie magic is similar to that of the Nym and we can go learn some stuff from the Pixies after they notice our Fairy and befriend us :3

For WHM... There's a new Forest zone right? What if that means another Elemental guardian who feels threatened by our arrival and we have to calm them down and help a Padjal get set up to be able to communicate with it.

AST... I have no idea really. As long as it isn't another lame story about some idiot and his Geomancy who keeps having problems that are solved with "Have you tried turning it off and back on again Astrology?"