Don't worry, someone will come in and make it a whining and complaining thread. But I do not know anyone who has done it or if there are any rewards from it. A really interesting idea I saw earlier on the forums would be a betrayal quest that allowed you to switch factions since the classes are "mirrored" anyway. Maybe that could reset your dark/light to neutral when you do that?
Personally it just seems like it would be easier to make a new character altogether than go from one extreme to the other.