If I were on the WWE creative team and had to accept Reigns winning the chamber with Finn set up to face Miz at Wrestlemania, I'd tie Brawn into a feud with Seth that kicks off with some sort of angle in the Chamber. Seth and Brawn can make each other look great in their own ways and both deserve a big match.
That one on one without a title, just to kill a feud is what Wrestlemania needs. One where the rivalry is so bitter that its personal, and not about any titles. That can be Seth and Brawn if they tell the story right. Somewhat like Seth vs Orton a few years ago, which I actually became quite vested in seeing and turned out to be a quality match.