I think he should cash in and beat Brock Lesnar after Lesnar is too tired from a match against someone. I know this is unlikely going to happen but just hear me out. Triple H decided to name Lesnar #1 Contender for the title against Cena back at SummerSlam after Orton was getting attacked by Reigns.
I know this did not mean Paul Heyman and Lesnar were working with The Authority but it showed that they had some relationship going on. It mainly just showed that Triple H would work with Heyman and Lesnar to beat Cena. If Rollins cashes in and beats Lesnar at a PPV and becomes a WWE World Heavyweight Champion then it shows Rollins did not just betray Paul Heyman and Lesnar but also The Authority.
Triple H gets mad at Rollins because he gave Lesnar the opportunity and thought Lesnar would keep the title away from guys like Cena or Ambrose. Rollins cashed in without asking The Authority figures and once against went on his own like he did with The Shield. This would set up Rollins turning on The Authority and becoming an individual rather then in a faction.
So to answer your question, my gimmick for Rollins would be a guy who is not trustworthy and more of an individual guy that is on his own. He betrayed The Shield and The Authority. He becomes champion and is now more of a singles wrestler.
I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.