As your parent pointed out, many places have a deeply entrenched culture of owners and mechanics illegally tuning vehicles. A speed limiter would not last long.

That's a problem for law enforcement and MOT inspections. Young people notoriously tune scooters and minicars already, there's absolutely no news there.

Penalties will take care of most of the tuners. For exampple, if you get caught with a disabled speed limiter you will have your license suspended for two years and your real full-power driver's license postponed by two years. Also insurance companies will impose hefty penalties if you're driving something else (more powerful) than what you've insured. If you crash, the insurance company will be charging you for the damages.

Here's a light-weight minicar after collision: https://is.mediadelivery.fi/img/1920/2965ca321c7a47758ca5a81... -- I'd rather have my kids take that hit in a passenger car, even a small one.

Then add a monitor? Inspect them (deliver them to registry office regularly) to see that they've been running at safe speeds only.

In my country at least, the regular vehicle inspections mandated by law are not performed by some theoretical incorruptible government office, but rather by the same mechanics who are willing to perform the illegal modifications. You can imagine how well that works in practice. (Which is not to say that I don't agree with you in theory, but people don't work that way.)

Make it digital then. Upload the device to a website using your cell phone. Nobody between you and the verification that way.

And if you don't upload, the car won't start and you get a call from a friendly community officer to find out what went wrong.

Agreed. In addition to making the world worse by having more cars on the road, we can also make it even worse by establishing a dystopian surveillance scheme.

...for 14yo drivers...