Here's an attempt: https://github.com/nostr-protocol/nips/pull/1591

Minimal (no) changes required of NIP 29 clients, although it's going to be a pain for me. The one addition to the semantics is that shallow reply hierarchies be explicitly encouraged, since I don't want people missing replies as a result of which client they're using.

This is just a first step toward merging the two specs. This is the easiest place to start. Maybe rooms can be merged with h tags later, although I'm less optimistic about that one.