I'm not sure you can start being selective about what people can do after they come out of prison. The idea is you come out having been punished for your crime(s) and hopefully rehabilitated. That may often not be the case but its the theory.
Is it that he will be a celebrity? Don't think so, he won't really be a celebrity at the level he'll be at. Is it what he will be earning? Seems more likely so on that basis wouldn't that apply to any career. If someone studies to become a brain surgeon while in prison should they not be allowed to take up that job as they will earn to much?
It's difficult because of what he's done but I think you have to change the system across the board, you can't selectively apply what you feel is justice.
Of course if the supporters of any club who show interest in signing him say they will boycott it is unlikely he'll be signed so that's probably the best course of action.