Beside the fact that it is impossible, I had an idea pop into my head.
What if he gets kayfabe injured, or something "comes up" where he has to leave indefinitely, preferably after losing the title or having to vacate it.
A few weeks later, have promos for a new masked huge wrestler in the style of Matanza or Mil from LU, but obviously his attire can't show any signs of him being Roman. So cover up all tattoos and hair and shit.
Book him well, preferably as a badass heel who NEVER talks. Have him use new moves instead of superman punch and spear. Do everything to make sure people don't know he's actually Reigns, or at least aren't sure.
Assuming he gets over with the crowd, be it getting proper heel heat or the crowd actually cheering him because he has been booked entertainingly, eventually have a match where someone rips off the mask to reveal it's Roman. The crowd, who has booed him for years, is shocked that this new guy they came to like is actually the guy they used to hate the most. MAYBE have him cut a promo on how he's sick of being the moral good guy (this is very optional since Roman + mic = disaster). Other much better option is to claim the injury made him mute, so you'll never hear him talk again (crowd goes wild lol).
That's just a ridiculous and unrealistic way of possibly getting him over or having him booked better. Just making him less fucking boring and not have him talk much, if at all.
Any other ideas?