Just throwing this out there, even though I'm not sure how I feel about the idea myself. Basically, new sets of enhancements that completely change what a power does.
For instance, Empathy's Regeneration Aura accepts Healing sets. So, now there is a new Healing set called "Transmogrified Damage" that can be slotted and changes it from a PBAoE heal to PBAoE damage. Or, "Transmogrified Defense" for a PBAoE defense buff.
People will ask how this can get misused, or how farmers are going to exploit it. Dunno. Thought up while shaving. Didn't put a lot of thought into it.