I know your guys are probably working on new updates, but one thing i think would be cool to add would be armor sets.
Usually these provide added boosts when you have most or all the pieces. So for a tank, if you had all the pieces it would add 20% more defense or something like that.
Also, I think it would be even cooler if it changes the overall look of your character. It would say it would mostly be cosmetic like a color swap so it would be easier to add, but would provide some visual feedback.