Most have already been said, but w/e.
1. Third tier classes, remove reclassing completely. Or at least not infinite reclassing.
2. Skill capacity. Could help with galeforce being too OP. Especially since it pretty much destroys the need for dancers.
3. Give snipers and swordmasters their innate crit bonus back. And keep the xxxfaire skills for classes locked to one weapon type.
4. At least 1 completely new map objective. Nothing anywhere near similar to current objectives (Sieze is pretty much the same as defeat boss).
5. Light magic, etc.
6. Auto promote at level 21.
7. Elevation bonuses and breakable/interactable terrain.
8. I never really used them, but I would kinda like to see those shine barriers return. Interesting concept and great for defend chapters.
9. Discussed to death, but pair up nerf. Love the concept, but horribly executed.