Hey  @provoost! Thanks for taking the time to write this up. I was thinking the exact same thing. I have been in touch with various MLS folks (both those working on the spec but also those working on the OpenMLS implementation). They are open to the idea and suggested that we create it as a custom ciphersuite so we don't have to wait on IANA to give us an identifier. 

For now, I'm more concerned with getting the rest of the NIP finalized and implementing it with the default ciphersuite to make sure that we have a working solution. As you say, we can deal with the custom ciphersuite later and upgrade groups. 

 I suppose that for a prototype the default-mandatory ciphersuite is fine. But I would hold off on finalizing the NIP until we have custom ciphersuite. Otherwise every Nostr client out there starts pulling in random dependencies from all over the internet.

... (well that might happen anyway, because you can't stop people as soon as a prototype works) 

 Let's get that IANA request done as soon as possible. It's simple paperwork, but it takes time to go through (months).  

 You have any experience with that  @Vitor Pamplona? 

 Not personally, but close colleagues did a few of those. 4-5 months to get a response.  

 As soon as possible, but not before the cipher is well chosen. And that should depend on actual implementation experience. 

 I also don't think there's much of a rush. Once there's an "official" number assigned, we recommend that clients use it. But until then the private usage number is just fine.

What is most useful I think is to have more eyes on it, which the application process should achieve. And it's nice to have things buttoned up eventually.