I've just thought about it, so forgive me if there is any inconstency on the "theory". Why I thought of it?
1- Orihime survived at least one hollow attack(her brother), not sure if that was enought, but anyway;
2- When Kazui transforms into a shinigami he doesn't leave his physical body, just like fullbringers;
3- About Kazui's shinigami robe: on his right arm we can see some flickering somthing that resembles Ichigo's second fullbring form; also it seems to overlap his clothes making the hoodie visible, again, resembling Ichigo's second fullbring form
4- Also I think his zanpakuto is not an real asauchi, being (like Ichigo's before the dual Zangetsu) a physical manifestation of his shinigami powers, in this case using the "fullbring" as a catalyst
Concluding, I think his "fullbring" ability would be to simply access his shinigami powers on his physical body.....don't know if it makes sense or if it's possible...