DNS records are increasingly used for functionality beyond IP addresses. Much of it is equally applicable to onion services: CAA records are a good example, as certificate authorities are now allowed to issue domain-validated certificates for onion addresses.
I feel this is a relatively easy feature to add, at least in a limited capacity: specify DNS records in the torrc file, and upload them with the other service descriptors. When resolving DNS queries through Tor, Tor could then fetch those records instead of going to the actual Domain Name System.
If necessary, DNSSEC is easy too: use the onion service’s ed25519 key to generate DNSKEY and RRSIG records. You can skip the chain of trust back to root, for obvious reasons.