> SHA-3 (or better, the Keccak permutation)

SHA-3 is just Keccak with specific capacities. If you mean that they should not implement only the standard SHA-3 functions then I agree, having c/raw/SHAKE256 as well would be nice.

Implementing the permutation would be even better, because other stuff like Strobe, Keyak, Ketje, etc... could use it.