[aesh2Xa1]

Another HN user, tptacek, has made comments going back years now that point out how modern Android (at least Pixels) and iPhones all isolate the baseband behind a serial/USB peripheral interface. I'm not sure you would gain anything at all by going with your surmised setup above.

[tata71]

Many carriers do OTA config stuff when you insert their SIM,

cooperated with by your carrier.