There already is a "tax" on players not sold -- they're messing up your fan survey.
It seems to bring one element of the survey down while bringing another up. Although I do not really understand what goes into those two elements (not afraid to be transferred and owner is working hard to improve the team). They seem to just be the opposite side of the coin... (even something as benign as bidding on a player but not winning the auction seemed to affect both for me)
Although maybe some things affect one but do not affect the other, I do not really know.
Run of the Mill Canadian Manager