Honestly, anything inspired by Amano's designs. Like the Moonward sets being inspired by the FF4 cast (is not an actual replica, but pretty close).
I'd love a new collection to contemplate more people:
Fending/Maiming, inspired by Golby. We already had Cecil Paladin, and his Dark Knight version we also already have the helmet and very similar alternatives. Kain is way too Dragoon-y to work as a generic tank set though.
Striking/Scouting, inspired by Yang:
Aiming, inspired by Rosa (I know, healers would probably be mad at this, but Rosa is also an archer...):
Healing and Casting, inspired by Palom and Porom. This seems like a really obvious choice because the original material is already recoloured with minor differences. Plus for once a set that would look best on Lalafells before anybody else
My other candidates would probably be FF7 Remake outfits... Maybe Barret and Tifa and their hairstyles, not genderlocked.