Yep, it's definitely a dynamic we have never seen with the MITB briefcase or in general really, and it could be made even more more interesting by the fact that Rollins would and could presumably be nearly as banged up as Lesnar/Cena (depending on who wins of course) when he would theoretically cash in, which would mean the match might not be the normal insta-route curbstomp (no pun intended) matches we are accustomed to seeing with the MTIB; through another interesting scenario would also be Rollins just outright winning the Triple Threat. Would he lose the MITB briefcase automatically then or keep it in that case?
Of course, the odds being so stacked in Rollins favor could all just be a swerve and Lesnar or Cena could still walk out with the belt and Seth could still lose the briefcase in either case; through at this point I am still leaning towards and predicting that Seth will be walking out of Philly with the belt when it's all said and done.
Rollins is a smart guy though. He could not get involved much in the match. Feign a knockout and let Cena and Lesnar go at it. I'm sure neither guy will have their minds on Rollins cashing in. I mean why would he? He could let those two beat the hell out of each other while he remains "knocked out" , not factor in the finish and then cash in.