Much respect to Michael Spinks for not going down that path. He saw what happens but still it's not easy.
Unfortunately for Leon, the cruiserweight division didn't exist until late 1979. But if it had, the 190 pound weight limit might have helped to keep Leon disciplined, or conversely, it might have been too light for him and he would've naturally grown into a heavyweight anyway. Had it existed then, with a weight limit of 200, it might have been a good option. Leon would've surely been competitive, likely would've won a world title, and yet not faced the societal scrutiny that the heavyweight champion faced at the time. He could've made a really good living. That said, I'm afraid his lack of personal discipline would've derailed him even if this option had existed.