so theres a nostr based name resolution in the relay side? And you need to announce the relay that host the webapp (that most probably has his static ip)? That seems to reimplement dns on upper layer, doesnt go beyond it. Or I lost something? 
If I correctly understood, I see two advantages here:
1) every npub can sign their own entry on the hash-table to be reachble without requiring third party dns-like trust.
2) ip static decorrelated from webapps for a better censorship resistance.