#4 Mark Henry
Mark Henry still hasn't officially retired, but it seems unlikely that we'll see him back in a WWE ring anytime soon, if ever. He's spent the last few years wrestling sparingly and putting over talent like Neville whenever he can. But if he's going to remain under WWE contract as an ambassador, he might as well be a manager while he's at it.
Henry has always been solid on the mic and is one of the most well-respected superstars of all time. He would bring with him an aura of credibility and legitimacy, which would then rub off on whoever he's managing. For Henry, it would probably make the most sense for him to manage the next great giant in WWE so he can take them under his wing. Of course, Braun Strowman is already doing quite well on his own, but there are other candidates.
The best options are in NXT, where a few superstars fit the bill. Lars Sullivan and Killian Dain, should he separate from Sanity, would both make sense. And in the tag team division, Heavy Machinery could use the rub they would get by having Henry alongside them. All of these guys would benefit greatly by being on screen with a WWE legend like Henry. If WWE is smart, they'll pair him off with someone in the near future.