I'd be ok with this whole half-Grimm thing if they were doppelgangers and not the people reincarnated. No personality, no memories, no intelligence. 100% raw savagery of the Grimm with a familiar face. The physiological effects alone would be devastating, and that makes it seem right up Cinder/Salem's alley.

I can imagine them returning as duo of twisted versions of their former self, Pyrrha tries to argue that killing humans is bad but keeps doing it, while Roman argues that it is a pleasure to do so, while he also keeps killing humans.