I wanted to vote on almost all of them... Too bad I coult only pick one.
But serious, we need:
Harder modes/levels
Extra story mode
Expansion for those over level 100
In-game trading (not really needed but would be cool)
Chat functionality outside of guild (yes, and improve guild chat, fact that everyone uses line says enough)


Also, at the smith and fusion building, place all the same armors together and give them the sum number.
It really sucks when you are saving fusion boost armors or low star armors and you need to scroll pass them every time...