I'd say, if you wanted to have a wizard(ess) that bound him/herself to an emotion sucking demon, then it'd be perfectly fine. That's all that a WC is, when you get down to the bare bones of it. We have precedent that one can bind themselves to demons
Hexenwolves, Denarians, etc
so that part is perfectly fine, in my head. Where you get into unsteady waters seems to be in using the same exact demon that the WC are bound to.
The way I'd do it, is have my character bind him/herself to a demon that promised something similar to what the WC have. I could see a wizard(ess) that was enamored with the WC, having a quest to become like them. However, I'd have there be a catch to it. Maybe they're nearly unable to control the powers they gained. Keep in mind that Thomas, who's had this hunger for at least the past ten years, is nearly unable to control it. Could you imagine all of a sudden being opened up to a hunger that you've never had before? Maybe the hunger has sapped their magical energy or it's tied to their magic in some way now. Also, I'd say the kind of person that would
want to be like a WC probably would be more than just a little unhinged.