Don't know what Sting could provide at his age, Lord knows I am dying to see him return as the muted Crowd Sting. A match with Undertaker at WM won't do justice as we know he wouldn't win - coupled with the fact that outside of the initial intros/epic staredown that shyt would be
What I would rather see is Undertaker in a program going into WM. No promos of Sting or anything, regardless if we know he signed. Taker gets outnumbered at some point in the match and that's where the lights go off and dude drops down from a Copter or comes through the crowd with his OG Crow Sting music (Eagle in hand).
That pop would be nothing short of insanity

He cleans house with his trusty Louisville slugger and helps Taker get the W. That closing moment alone would be
Not sure I'd want to see him in an actual weekly program unless done right.