As the title implies, a cool suggestion would be a harcore mode character option!
These characters will require 3x the exp of normal characters BUT they would recieve special rewards every couple levels, unlike the anniversary box which is every 5/10 levels.
Among other things like special drops from mobs, and ,maybe even a special instance area that only hardcore characters can enter which would drop those special farm-able items.
I know this will put a lot of people off because of the already increasing exp curve after 60, but people who have played DOMO for a long time might find it fun!