Kei cars have significant concessions for side impact protection because they have to meet a strict width limit. Those concessions fail minimum standards in quite a few markets that don’t normally consider the class. Kei cars can only be 1480mm wide, a current Fiat 500 is 1683mm.

Agreed. The above post is downplaying the legitimate risk. *That said*, motorcycles are legal and they're far worse, so... I think so long as you have a registration system that makes clear you're lowering your safety, they should be allowed.