User blog comment:Collbrande-Ex-Caliburn/Hyoudou Issei's Peerage composition hopes/dreams/hypothesis/@comment-10330822-20161112235347/@comment-10330822-20161121054153

Yeah, the concept was introduced when the Brave Saints were introduced. The problem is, we don't know whether the research is close to being complete or not. Or, for that matter, if the research can even be completed now that Azazel is sealed.

It's true Issei could possibly trade Michael for Irina even with Michael sealed, but the problem is if the research isn't completed because Azazel's there, then someone else would need to finish it for that to even happen. Otherwise, Azazel would need to be freed before the concept can be realized.