Some kind of buff that immediately upgrades an entire subclass
But it only works if you already have the same elemental subclass upgraded on another character, and will only upgrade to the point that your other characters subclass is leveled up.
It won't hurt the game, it will just make the things that people need on their other characters available to them without the need to grind things they've already done just so they can grind more for the good stuff. I think it would make for a more fair environment and give people more things to do (having more characters that don't take forever to play at their fullest).