Affliction changed to a healing spec. DoTs and leech based. Similar to how the concept of a disc priest is that you need to dps to heal.
Destruction completely gutted and changed to chaos. Purple and green fel spells. Give Fire mages immolation.
Demonology locks could have a 10-min CD where they turn into a larger version of the minion they have summoned to assist with DPS or crowd control. More demons to choose from when summoning.