Only way to salvage this IMO:
-Lesnar does something henious to Reigns, like attack his family or something
-Rollins cashes in and wins the title
-Reigns wants at Brock so bad, he gives up the title shot just to fight him at Mania
-He gives it to Bryan, who "never lost the title" on the condition he gets a shot down the line when he wants it
This sets up either a huge Summerslam main event, or a big match whenever Reigns is ready. Maybe even a Reigns heel turn if they want (he is mad he let Bryan take his spot and goes on a rampage, for example)