This idea just came to me, just thought I would like to see a discussion like this going.
Things I'd like to see:
*Seeking Party Feature
*Several mobs not yet added: Mandragoras, Lamias, Soulflayers, Iron Giants, Shadow Dragons, and Wyrms. (Not to be confused with Drakes)
*Housing. (Much like MogHouse)
*Endgame events similar to that of Assault, Limbus, and Salvage. (those were fun)
*SUSHI!
*Conquest (I always thought it was fun to see which zones get dominated by which nations).
(Yeah yeah in before 500+ post of Auction house please, along with chocobo and airship)