Is there a good reason why we cannot simply disable Android Carrier Privileges? By which I mean permit handset owners to make changes to VoLTE and VoWiFi etc. settings without needing to have the carrier push these out, else install a specially signed app, where a hash of the signing key is stored in an ARA-M applet on the SIM card.
I cannot see how this would compromise security and it's beyond annoying to have such settings off-limits to device owners. It's also even more of an issue with the advent of mobile private networks, e.g. using CBRS band and similar in other countries, where you could easily be running your own IMS.
I'm not aware if any other Android operating systems do this, but presumably it would just be a matter of overriding default AOSP behaviour.