My guess would be that your car would develop some covert or overt fault if you did that. You might even lose warranty as the manufacturer could claim that the issue they fixed via a software update couldn't be installed on your car - or couldn't monitor some diagnostics which are a prerequisite for in-warranty repair.
Most telco execs would sell their own mothers before offering reasonable data plans - that your car comes with one for free should be very telling
> My guess would be that your car would develop some covert or overt fault if you did that.
I used a bypass harness to avoid losing a speaker and the car hasn't developed any fault. I wouldn't buy a car without knowing in advance that this mod is possible. There are plenty of tutorials on how to do this for popular makes/models. It may be as simple as removing a fuse, or you might need to disassemble part of the dash to physically unplug the modem.
I'm a but skeptical if this is going to be possible in the future - I'd say it's increasingly unlikely that you'll be able to meaningfully change anything in your car.
For example if you look at where Tesla and co. are going, they are looking to reduce the amount and tickness of wiring harnesses - and they did so by creating a proprietary fieldbus that communicates between proprietary controllers that handle multiple functions, so they can multiplex everything under the sun into a single bus.
Most telco execs would sell their own mothers before offering reasonable data plans - that your car comes with one for free should be very telling