I really think there should be a middle zone between the quadricycle regulation (like the Citroen Ami, Renault Twizy, etc) and “normal” cars. Make a class for simple and cheap cars that are more capable than the quadricycles, but still have some conservative power and/or speed limits, size limits, and some safety standards.

I’m imagining a class of vehicles that are like a modern take on the post-war economy cars like the Fiat 500, Citroen 2cv, VW beetle, etc. Something similar to the Japanese kei cars, but probably even more restrictive on power.