The bracket is funny because it doesn't even pretend that Roman will have any sort of challenge. As far as his opponent goes, it's Owens vs. Ambrose in the final. Owens seems like the obvious choice due to being a heel and being more than fine being with The Authority for money. Ambrose may have more intriguing storylines as far as turning heel goes.
Can't seem to go wrong with either scenario, but I still wouldn't give it to Reigns yet. It's a Wrestlemania moment, not a thrown together one. No one wants to see the face champ defend at Mania, they want to see him win it there.