And passkeys. Don't forget passkeys. Trivially to implement in some kB of ROM. /s

You jest but there's no reason to stick with twenty year old component restrictions in a car that costs forty grand.

The real cost will be in the software validation and road safety hardening, but there's no reason why the ROM size should be limited to kilobytes.

You can implement full passkey cryptography on a basic esp32 (https://github.com/polhenarejos/pico-fido). Cut out the cruft and you can definitely get a similarly secure algorithm on an actual car key or key receiver.

And honestly, with cars now unlocking over Bluetooth and WiFi, standardising that process to something like FIDO wouldn't even be that awful of an idea. It certainly beats the "we can do cryptography at home" many car manufacturers seem to be going for.