If they do bring Sting into the WWE, even if it's for a single one time match, how do they do it?
The simplest way would be to just do a tag team match with Sting/Bryan Danials vs Flair/HHH as they can play on the history between Flair and Sting, hide Sting's ring rust via a tag match scenario, and moreso, have his arrival mean something big as far as Bryan thinking outside the box and purposely recruiting Sting as a partner to go against Flair and HHH as far as far as hitting them with a mystery partner who HHH can not bully or threaten or extort (and who would know Flair like an open book to counter).
That's the simplest way?
I was thinking more that they announce him for the Hall of Fame and someone (let's just say...Moe?) gets all upset that he's never even had a WWE match before, and challenges him to said match at the Wrestlemania.