User blog comment:Collbrande-Ex-Caliburn/Hyoudou Issei's Peerage composition hopes/dreams/hypothesis/@comment-10330822-20161112235347/@comment-10330822-20161113140039

Except you fail to realize they are already getting married. Issei's social status is the same as her's anyway. Besides, we all know that pureblood-racism crap is going to be solved in this story. If Issei becomes God-status, than there is literally no arguement to why Rias can't be his Queen, he is already physically far and away stronger than any of the other High-Class Devils.

You are forgetting though that Issei is already her Pawn. So its already causing a conflict. Chances are they can't compete at all against each other at this point at all. However, in the WRG's, they have fill in pieces. Mr. Black is standing in for Issei, so he can fight Rias in the WRG. That is what I am saying. This maybe the only chance Issei really gets to fight Rias and prove his worth.

What I was referring to is an Brave Saint being traded for an Evil Piece. When the Brave Saint system was still under construction, Azazel said they would be looking into way to trade with the different piece systems. So Evil Pieces could be traded with Brave Saints, and vise versa.