User blog comment:B214/Volume 22 spoilers/@comment-82.48.158.172-20161109231053/@comment-10330822-20161112224125

I only thought Kunou would be interesting, I never expected him to actually get her.

I highly doubt Incinerate Anthem's holy relic properties being relevant. By that logic it doesn't make much sense for Valerie, who is part Vampire, to be able to use the Grail. Likewise, you can adjust a holy weapon to be used by demons, like all the alchemy that was used as Ascalon for Issei to use it. Also, Xenovia and Kiba also seem able to use holy swords, like Durandal and Excalibur, and when it comes to Durandal, Kiba isn't the intended user.

Incinerate Anthem is indepedent of its users, that's why it can shift from user to user, I'd see no reason it can be adjusted or played with like a holy sword.

When it comes to Issei's peerage, my main point was that you can't have newbies in there, because everyone is already Mid-to High-Class Devil level status. In order for these guys to get stronger and keep moving up, they can't have weak sauce newbies. That is why if Issei makes new devils, they need to already be very powerful in some regard. A Longinus user or a Pureblood Vampire just seem very well-suited for this.