I don't think Madine carries the reputation outside of Sheffield that he does within it. He might be an unsavoury character but I very much doubt that the Club's reputation would be damaged by signing Madine on loan. I'd be more worried that he'd disrupt the team atmosphere than anything else.
However, I very much doubt Wilder would sign any player that he thought would be a bad egg though, especially given how well we are doing, so if Madine did arrive, and there's no news stories to back this up, then rest assured Wilder will have done his homework with several players and Managers.