New languages has already been suggested many times, but focusing on menus specifically should be easier to implement and very effective. By menus I mean like the homescreen, login screen, menu, avatar, inventory, character selection, maps, platinum store etc.

What I'm definitely not suggesting is every item in the game should be written in 5 languages, or all the quest dialogue is translated. Just simple one word stuff like <Avatar> <Choose character> <Armor tab> <Vanity tab> <quests> etc. thats imperative for navigating the game.

Just by adding a few more popular languages from around the world would attract many players