I just copied that approach to Nostr, I'm not sure if I thought Nostr was always going to be a single main flow (text notes) but it clearly isn't and hopefully it will grow to be even less like that. Nostr also clearly isn't like a single-implementation programming-language-spec with a dictator and his committee on evaluating random "improvement proposals". So we're forced to conclude that the numberered-documents approach isn't the best way to do coordinate the creation of Nostr-based sub-protocols.

It could be beneficial to create a new standards process in parallel that references the current NIPs without deprecation of the current repo or even process. What that means is that you can gracefully transition with minimum disruption for any current protocol design process.

If the new process doesn't work, it would be easy to try another solution. If it does work well, gradually move from NIPs to the new process.

That would basically allow point 2 and 3 of your proposal to just be done without the formality of point 1.