Just a list of things I think would make nice additions to the game's core mechanics that would provide longevity to existing features.

-Add a daily roulette for Deep Dungeon where you can queue into a random 10 floors and a set of random pomanders
-A daily roulette for Variant dungeons where you get put into a random V&C dungeon and a randomly chosen pathway. Maybe give the players 60 seconds to work out their skill choices.
-Let people queue into groups for FATEs and it just drops you into a random leveling zone downscaled and directs you to fates in order. Chaining them gives more EXP, gil and gemstones.
-Bicolor gemstones now drop from all fates, and can be used to buy all the same items as hunts
-More small scale additions to the Gold Saucer; card games, board games, perhaps a coliseum system to watch races and stuff
-Add a special instanced Ancient/Greek style amphitheater to the game. Groups of players can reserve time slots similar to how Eternal Bond Ceremonies work for this to host plays, story telling, comedy acts, etc. Let non participating players queue into seating to watch the hosted events.