Just to throw out some thoughts.
Enthralling, as I understand it means to bend someone to your will. To force your will onto their mind like some kind of mental handcuffs, no matter how gentle or how much they think they want it, would cause mental damage - probably the kind of thing that would snowball into something that would come to some form of insanity. Even if a person would want someone to take over, in no matter how small a way relieves them of responsibility for their actions. Acknowledgement of responsibility for ones actions is part of the whole of free will.
Rather than a brain surgeon the practitioner becomes the de-facto jailer in certain situations. Even in willing participants it wouldn't work. Some examples might be:
If I come to a wizard and say "I want to quit smoking but I just can't dredge up the will-power. Please make me quit smoking. It's killing me." The practitioner reaches into my psych and carefully takes away my urge to smoke. Sounds good right? But what he/she didn't know is that when I started smoking I did it to be like my mom, who also smoked. The smell reminds me of when I grew up and I find it subconsciously comforting. Now I don't smoke anymore. I also find myself feeling oddly uncomfortable talking about when I grew up as I can remember the comfort I got from my past but the smell that triggered the feeling is no longer something I enjoy. I stop talking to my mom (who may have quit smoking by now) because the acquiescence of my free will on the subject is chafing and she is associated with it. Can you see where this might go?
I come to a practitioner and say " I got bit by a dog one week ago and now I'm afraid of large dogs. Please take away that fear. I like dogs." He/she reaches in and takes away the fear but because I didn't work through it myself and did really want to not be afraid, I "help" the practitioner along and now I'm not afraid of any animal biting me and I decide I want to jump over the enclosure fence and pet the lions at the zoo because they look so soft and what the heck, what is everyone so afraid of anyway...
The brain surgeon analogy only works if most minds, like most brains worked in the same way. Medical science knows approximately where the speech and memory centers of the brain are - the basics of perception. The mind is something completely different, although some physical imbalances can cause similar mental instabilities, everyone has there own insecurities and hang ups that will manifest in unique ways. We won't even go into cultural differences, world paradigms, and ethical imperatives that could be bound up into something a practitioner might alter trying to help the person that would cause other domino effects.
Remember The Summer Lady was trying to stop an ongoing bloody war when she almost destabilized the world. She offered Harry her help in healing some of his mental wounds but without his reactions and coping mechanisms caused by those past traumatic events he would not be the quirky passionate guy we have all come to know and love.
The Fae are able to take things away without doing peripheral harm (remember Susan at the vampire party) - Good for them - but I don't believe we humans with our filters and flaws could do something like that so 'cleanly'. The practitioner reaches into my mind to help me stop smoking and finds out I don't like dogs because I was bit by one as a kid, which, as an animal lover, they see as a flaw so they fix that too...
As a soul gaze it might look like an infection in the soul - something small is poisoning the person slowly.
No I'm afraid that this particular law should not be bent and if a character does the GM could think of some bizarre reaction and the wardens should take notice. Not to say that people don't act bizarrely on their own but I think this one should be a stain on the practitioner’s psych as well.
Kristine