You've hit the nail on the head. The lack of a DMARC - like standard for transaction validation is a glaring gap. In a world where transactions can be manipulated or spoofed, having a reliable way to verify the source is essential. Just as DMARC revolutionized email security by validating domain ownership, a similar approach for transactions would protect users from potential fraud. The connection to AA makes it even more relevant, as the new models of transaction submission introduce new risks. It's high time we saw some serious proposals to address this issue and bring more trust to the blockchain.