Vinyl wrap with Faraday cage on the inside layer? A modern "cone of silence"
Hah, tinfoil wrapped car, for the tinfoil-hat crowds...
In many cases this isn’t viable. On my car for for instance - a 2016 Subaru - removing the telematics module also disables all front speakers because the audio signal is routed through it.
Sounds like a relatively easy problem to solve. Install your own sound system.