Things I would add:
Make the holy weapons more plot relevant
A Berkut like character maybe a female noblewoman who's the cousin of Sigurd.
Supports and Barracks
More Classes
Weapon types to existing classes
A animal shifter of some kind
Things I want to see:
Make Lewyn x Erinys one of the canon pairings Fe5 did it so can this remake
Azelle x Tailtiu maybe canon