I'm not quite sure I understand what this part means? On "current scemes":
> (d) lacking open access, not allowing anyone to create a namespace mapping.
This (finally) adds some amount of censorship resistance to LN Address, not to mention better security and (thanks to BOLT12) even allows users of custodial services to use their own domain for their address!
The full protocol (lightning-specific) protocol is implemented at https://git.bitcoin.ninja/index.cgi?p=lightning-resolver;a=summary nostr:note1gt9ryucy0eyn6gcez3vj5j2vgswsp70kz9mhk97egh54r4cjmzcsswpv06
Discussion
There are proposals to add proprietary APIs for, eg exchanges to expose the ability to pay their users but not users of other wallets, at least in specific contexts.