> small cores are arbitrarily given a burden of supporting variable-length instructions Even the smallest commercial microcontroller cores e.g. the CH32V003, s

> small cores are arbitrarily given a burden of supporting variable-length instructions Even the smallest commercial microcontroller cores e.g. the CH32V003, support the C extension. They strip out other things, such as half the integer registers, but they keep C. And that's in a market where you can use literally any combination of extensions you want, because the customers compile all their own code, and you just tell them what ISA string to use.