Hello @xmtp.domains - so great to see you here! 
I wanted to share that this proposal is out of date and that perhaps you’d be interested in this XIP, which is the current design: XIP-49: Decentralized backend for MLS messages
Also sharing an invite to the XMTP Dev Call on Tue Feb 11 at 9 am P, if you’re interested! XMTP Dev Call: XIP-49: Decentralized backend for MLS messages