Also just another thing that might be interesting:

Check out 'intermediate temperature storage', the idea of storing at a slightly warmer than liquid nitrogen temps (-130'C as opposed to -196'C) is a good idea in order to avoid any fracturing*. This is right near the glass transition temp, so no nucleation can proceed.

Tricky part is there aren't any practical scalable chemicals that have a handy phase change near -130'C, (in the same way that liquid nitrogen does at -196'C) so any system to keep patients there would have to be engineered as a custom electrically controlled device, rather than a simple vat of liquid.

Not impossible, but adds a lot of compexity. They might end up doing it in a few years by putting a dewar in a dewar, and making a robust heater that will failsafe down to LN2 if there's any problem.

*Personally I'm not concerned with fracturing, it seems like a very information-preserving change compared to everything else.