This system is already in use for lorries, which are hard limited (like the last option described in TFA — engine loses power if driver attepts to accelerate beyond the limit). It's an absolute hell for other users of the road, because they're hard limited to 100 km/h, even on roads where the legal limit is higher. Now the problem is, no two vehicles have exactly the same limit, it varies a noticeable amount, so inevitably one lorry driver will attempt to overtake another one — with speed difference below 1 km/h, at about 100 km/h where legal limit is 140 km/h. It takes about 2 min and usually causes 2-3 km "jams" on motorways.