LA Knight and CM Punk promo wise
Beyond that since the Hardys have worked in WWE recently I'd say Punk vs. Jeff Hardy again, but switch up the dynamics a bit. Ideally Punk would be the veteran babyface and Hardy would be jaded and spiteful. I know the feud won't get as dark as it could though. What I mean is the drug stuff actually playing into the story with Punk being the role model and Jeff wanting forgiveness for his past, but Punk refusing to accept that Hardy has changed. Jeff could snap on some "I tried to be a changed man, but you wouldn't let me be that!"
The feud could branch off into a Jeff vs. AJ storyline with AJ being on Punk's side playing off the TNA redemption storyline that they did years ago.