That makes sense to me. For example, if we do reactivate CAT similar PoW proofs could be done with plain hashes.
stack: <nonce> <hash_prefix>
script: <required_hash_suffix> CAT SWAP <preimage_suffix> CAT SHA256 EQUALVERIFY
(probably missing some details in ^ by allowing any length nonce, but it’s the general idea)
In short there are better ways to achieve this than ECDSA (which matches my gut reaction).