A'ight, so, I talked it over with a good bit of the staff, and the general consensus is a resounding "No" on the semblance.
In a nutshell, on one hand, there's too many major worldbuilding implications baked in to this semblance, including the idea of immortal Grimm. On the other, this semblance will likely never, ever come up in a thread. If it did come up in a thread, it would almost certainly be forced into the non-canon section, because the wider aforementioned worldbuilding implications would throw everything out of whack.
This also isn't a case of "Change a few things and we can talk about it", but an outright "This semblance won't be approved". If you have questions, feel free to reach out on discord, I'll do my best to answer what I can.