Make nip 05 providers also email providers. I realize this adds a large burden for providers if they want to provide an email client, but they don't necessarily have to do that. I made my NIP 05 (hodlbod@coracle.social) into an email address with an MX record. NIP 05's could do that with users' existing providers.

Lots of sharp edges there, but I really think the right UX is to have the same name for both protocols.