It wouldn't last five minutes on my car without being disabled. Easy to do, use a portable spectrum analyzer, find the source of the RF and then nuke the antenna.
Same goes for any other appliance that radiates RF signals (IoT, etc.).
You don't stop internet access or do anything to alter the electronics. By blocking the car from transmitting and receiving cell signals it's effectively the same as the car being out of cell range.
If cell access is essential, what happens in a place without cell access, much of Alaska perhaps?
I hate to think of all the lawsuits resulting from drivers who drive into locations where cells are out of range and get stranded.
Similarly, what happens when the cell phone system breaks down? And does that mean I can't buy a car if I live in an area with intermittent, weak or no cell or internet service? Hate to think what the manufacturer's sales department would think of that.
On the matter of reverse engineering, it seems to me we're just on the cusp of that. Hackers as still getting organized and aftermarket manufacturers have still to tool up for complete computer replacement kits. Reckon we're only at the very beginning of whole new industry.
Oh, I nearly forgot, the Right to Repair movement has only just begun to get organized. If manufacturers try to stop us altering something we've paid goid money for then they'll be in for a long political fight.
Same goes for any other appliance that radiates RF signals (IoT, etc.).