There’s currently only one save slot available; add multiple save slots.
Add an auto-save feature that saves after changing maps, before boss fights, etc.
An additional New Game + mode, where players can restart the game, using characters and stats from the previous saves.
The main story might feel too long for some people; make the story a little more compact and add sub stories and quests instead.
Implement a crafting system, which requires using material to create weapons, armor and upgrades.
The 3DS Friend system was a bit complicated; make it simpler.
Add a Square-Enix members achievement system for the 3DS that doesn’t require having to check the website on PC.