nostr:npub1084ge48f4zqjlw46vwazq3r6chmh8nfq6pcxvef8d3mnrkm3e7squ5700n Your criticism of RDAP is not clear to me. What could be sent by an information service but "bunch of information bits"? What is the regional convention you speak about? 
And about the difficulty to do it programmatically, sure, jCard is painful, but just finding the entry with ""roles": [ "registrant" ] is not to hard for a program.