User blog comment:B214/General Discussion/@comment-73.46.6.122-20161208211527/@comment-9595671-20161209150934

So future artificial gears could be powered the same way, not necessarily by the dragon aura Issei's kids inherit, but the powers that an individual can inherit. Especially the ones more specfic to a species.

Devils could power theirs through demonic power, angels and fallen angels through their holy powers, youkai via their chi networks, etc. Azazel's method did require power sources too, but usually they were ones not specific to the user, perhaps that's where the problem lied.

True Sacred Gears are given to someone at birth, so it would make sense to say that the ones who have them have a power compatible and meant for that gear. In fact, I guess you could say it's the natural version of Euclid's method.