User blog comment:Jopjopjop/Volume 19 Spoilers/@comment-3965848-20150802144453/@comment-3965848-20150802160332

1.Kiba's BB is revealed to actually be an irregular not a subspecies.

2.If Issei gets a subspecies I assume it be some sort of King armor form, relating to his ability to change his armor into varies chess pieces and desire to be a Harem King, that's just my guess.