Final fantasy games have always been visually stunning and usually introduce a world that is very foreign yet unique i think there should be additional class quests for jobs like paladin and summoner, where like you fight someone or something and receive a weapon, thus unlocking the class, because it seems like a lot of the reoccurring themes are missing from the game. summoner was one of the classes that seemed to be iconic of the franchise yet is missing from the game.
i would also like to see a game like tetra master in game... or some lore oriented activities such as gambling maybe chocobo racing where players race them themselves and bet on their friends, chocobo raising also...
maybe seals or some special items that can be redeemed in an arena area where players fight monsters and maybe each other.(like an old currency) also similar to campaign, in final fantasy xi, maybe there could be aetheryte sieges from beastmen similar to behest....and i think there should also be beastmen territories or maybe camps.
The animations for spell casting should be changed to be bigger and way more elaborate the sigils used through out the Final fantasy franchise during summoning should be used i think.