I'd personally prefer if they were completely prohibited from sale, the law being that a fitting centre that removes an old tyre must render it unusable by a section being cut out. Any person or centre selling part-worn tyres to face imprisonment.

The safety implications are huge. It's not just your life, it's your passengers, other road users, pedestrians, the lot

Dive cylinders that fail their tests, a section is physically removed, and the thread is attacked with a hammer and cold steel bolster. That way they can never be re-used.

If such an approach is sensible for a dive cylinder, where one is the likely casualty list, then such an approach must also be sensible for motor vehicles with multiple casualties/fatalities possible (and far more likely) in the event of failure.

Going off at a bit of a tangent. If your tyre gets punctured by a nail close to the sidewall and you then fill the tyre with the manufacturers sealant and drive off. What would be the reaction of your insurers / police if you then lost control shortly after due to an under inflated tyre?

I would guess they would be within their rights to say the car was being driven in an unroadworthy condition.