Hmm. So it's OK for the government to dictate what features a car must have, may have, may not have, etc? And the government should also inspect these vehicles

Hmm. So it's OK for the government to dictate what features a car must have, may have, may not have, etc? And the government should also inspect these vehicles and make sure they meet the standards before allowing them on public roads? Well, turns out you are in luck because this is all already possible in the US. Pretty much everywhere there are provisions for one-off custom vehicles and getting them inspected. Sure, the paperwork is daunting and the process isn't always easy, but it is definitely possible. See article about an engineer who registered a jet turbine powered VW bug that shot 15 foot flames out of the back of it in CA that surfaced on HN a few years ago. But we aren't necessarily talking about one-off cars that hobbyists who care about their craft create. We are talking about Walmart popping out $1,100 golf carts without airbags because it's a "city car".