Board Thread:General Discussion/@comment-26064296-20160712051823/@comment-28044177-20171004024303

Soul Suicide occurs when the boundary of one's soul is destroyed. The only known method that destroys the boundary of one's soul is Hollowfication(the process of obtaining Hollow powers). Because of this, Visoreds(Shinigami who obtain Hollow powers), need a vaccine that contains essence of Quincy and Human to prevent the boundary from being destroyed. This would also prevent them from becoming true Shinigami/Hollow hybrids, and just become Shinigami with some Hollow powers. It's even more dangerous when it comes to Quincies who obtain Hollow powers, because even if the vaccine prevents the boundary from breaking, the poison that Hollows give to Quincies would still kill them. This is why Kisuke needed to tie Isshin's soul to Masaki's to completely suppress the Hollow power inside her.

This would be different for Shinigamification. Arrancars, Hollows who obtain Shinigami powers, don't have the risk of Soul Suicide because Shinigamification doesn't destroy the boundary of the soul. And in the end, they're just Hollows with some Shinigami powers, instead of perfect hybrids. The only one who has ever been a perfect Shinigami/Hollow hybrid is Aizen, with the help of the Hōgoyku.

Back on topic. I believe it would be impossible for a Quincy to also be a Fullbringer. Or should I say, it would be impossible for them to use Fullbringer abilities, since anything Hollow inside of them would need to be completely suppressed in order to keep living. That being said, Fullbringers only have trace amounts of Hollow in them. So maybe it wouldn't be enough to kill a strong Quincy. But as a baby, it'll probably have some kind of reaction.