I like the Bullet Club idea, but I don't think Balor's entrance would work as a surprise debut. It would look dumb as hell if they paused the match for like 10 mins while he did the Demon shyt, but if it was just a surprise attack thru the crowd that could work.
I would do it where Shane is getting his ass kicked by Undertaker the whole match, just thrown around the cage and shyt, but Vince is at ringside and keeps telling Undertaker to prolong the punishment and not pin him yet. Undertaker is reluctant and wants to end the match, since he has no personal grudge with Shane, but his boss is telling him to destroy Shane and not end it yet. This is how I would get around the fact that Shane isn't really an active wrestler, so it would be dumb for him to have a competitive back and forth match or kick out of any finishers. You get across the story that Undertaker could end it whenever he wants, but Vince won't let him. All the stalling and Vince arguing with Undertaker gives Shane a spot to finally get the upperhand, where he hits a couple of high spots and the vanterminator.
Vince panics and get some Authority henchman out (league of nations), but you get a surprise return from (in a perfect world, Stang, but if he's still hurt then Cena), Cena cleans house and hits the AA and then goes face to face with Vince outside. Shane capitalizes with some move off the top of the cage or some shyt to get the win.
Shane wins, but it doesn't really hurt Undertaker at all, and you set up Undertaker-Cena for possibly Taker's final match
