For me the point of a pressure relief valve or PRV (what we call them in automotive) is that sh$t happens and things can terribly wrong. People monkey with their cars, they bypass control devices, they overcharge, unexpected failures and consequences do happen.

You can either have a psssst of refrigerant that is puzzling, or you can have ruptured components, collateral damages, and hurt people. You're going to loose the refrigerant either way. I wouldn't design a system that my child may someday drive that doesn't have a PRV (not that anyone would let me do it anyway).

I think the way blank god's doing it is just what ASME or his NZ equivalent would demand for a pressure vessel. A PRV that pops at or below the rated working pressure of the various pressure vessels, and vents to atmosphere.