How 'bout...

Lesnar pins Reigns cleaner than a communion dress at Mania. Lesnar announces on Raw that he is leaving with the belt and to hell with us all.

Rollins saves the day by announcing that Brock isn't going anywhere because he's got a briefcase that says Brock has to defend one last time.

You know the rest. Phone Post 3.0

Don't mind it, but the way Reigns has been built is that if he can't beat Brock, how will Rollins do it?

Coming in like that is basically a face turn, hence he 'should' go it alone without Noble and Mercury running interference. May not be the case and maybe I am being too old in that thinking.

Where to from there? Does Rollins denounce his link to the Authority or does he stay there? Who does he feud with from here? Is there a HHH run hidden in there somehow?

Definitely not against Rollins cashing in, but for the build of the storyline of each character involved, he needs to do it cheaply and with a good amount of cheating. If Brock stands up and basically tells us all to go fuck ourselves, he's putting Rollins into the saviour role, which in not sure is great right now. Phone Post 3.0

To prevent Rollins turning face, have him somehow lose the case to Ziggles or Bryan and then proceed with your storyline.
Then,
First challenger is Rollins. Phone Post 3.0

No way Rollins comes out and cashes in on Lesnar straight up, man to man like that. He's a chicken shit heel, he'd have to cash in like one. But him cashing in the night after WM would be cool. Phone Post 3.0

For a short while I thought that Bryan was going to win Wrestlemania and go on to beat Brock then lose it either right after or the next night to Rollins. Phone Post 3.0

MMAhaiku - Lesnar pins Reigns cleaner than a communion dress at Mania. Lesnar announces on Raw that he is leaving with the belt and to hell with us all.

Rollins saves the day by announcing that Brock isn't going anywhere because he's got a briefcase that says Brock has to defend one last time.

You know the rest. Phone Post 3.0
The problem with that would be it will turn Rollins face Rollins saving the day is a completely baby face move so he wouldn't do it Phone Post 3.0