Actually, they should add PVP. They should also make the following additions:

-- Some sort of delivery system so that items and gil can be sent between characters without them being in the same place.

-- A special zone, kind of like a house, which each player can customize to his or her specifications. You can change jobs, take delivery of items, access storage. Since this is a Final Fantasy game, I think it would be cool if you centered it around the ubiquitous moogle characters

-- A mount of some sort for travel over land. Again, since this is Final Fantasy, chocobos seem like a natural choice.

-- Airships, like in Final Fantasy 9, used for moving between major cities. For simplicity, route all this through a central transit hub, such as Jeuno.

-- Some sort of central clearing place, such as an auction house, where you can buy and sell items.

-- Instanced notorious monster fights that you can fight in exchange for treasure. In order to access these, have regular monsters drop some kind of token, and with enough of these tokens, you can buy something that will let you in to the instanced fight.

That's all I have for now. If anyone else wants to kick in some suggestions for adding things to the game that already exist, feel free to jump in.