User blog comment:Omega64/Boosted Gear Sub-Species Ideas/@comment-30048084-20161114190256

A sub-species that does not relate to dragons is impossible, Vali is the Dragon Lucifer while Issei can be seen as the dragon god. Issei is also technically a dragon himself. If anyone would receive the ability to steal other abilities it would be Vali.

If we look at Ddraig and Albion using Rating Game method Ddraig is a Power/Technique/Support type while Albion is a Wizard/Technique/Power type in order of strongest to weakest attribute.

Issei's best option for a sub-species would be to allow him to draw on Ophis's power from his initial balance breaker and allow the strength to scale up with each successive transformation and hopefully reduce the side effects of [DxD] G. Increasing the number of abilities he has while not interfering with his current irregular balance breaker would be a safe option.