It's a good start but in the era of EVs with infinite starting torque we also need acceleration and jerk limits. There's really no rational justification for why a car driving on a public street should have any sharper throttle response than what you get from a Toyota Yaris in "Eco" mode.
Hack the road by installing a fake 10 mph sign on a highway
It doesn't even have to be installed, you can project a fake speed limit for a few milliseconds and the systems will accept that. https://www.nassiben.com/phantoms
New trend: Walk around with a DIY stop sign so that you can cross the street when drivers don't respect crosswalks.
I mean, the barrier to using a fake sign or using a marker to vandalize existing signs is much lower than projecting an image from a drone. But cool idea tho.