Interesting! Couple impressions:

The same could be used as NIP-05 on nostr. The reality though is that when you have a domain, you usually also have a server (but maybe this makes it worth getting a domain without server?) Also changing DNS records with your registrar is often more pain than just updating a static file on the server. And finally from client (e.g. mobile phone) perspective - isn't it sometimes harder to make DNS request compared to HTTP? And I think for backwards compatibility, the client will have to do both anyway - first try DNS and then LNURL http...