#1. Not building towards Roman Reigns Vs. Dean Ambrose
The circumstances surrounding Dean Ambrose's pre-announced impending departure from the company, his actions as a heel after Reigns' cancer diagnosis and Reigns' return and subsequent Shield reunion have given WWE a unique opportunity to tell a story worthy of WrestleMania.
With that in mind, it would be a shame if they continue to play out the Shield reunion without any swerves, like Ambrose turning his back on Rollins and Reigns yet again at Fastlane. You can then have Reigns try and win Ambrose over and perhaps even convince him to stay in the WWE. Personally, I'd have Reigns Vs Ambrose with Ambrose staying in WWE if Reigns wins (Obviously this all depends on Ambrose's real-life inclination to stay with WWE, but we'll see)
A top AEW star just called one of his colleagues 'spoiled' and 'narcissistic' HERE.
Honestly though, what else do you do with Reigns at WrestleMania?