I understand your concerns regarding metadata aggregation. SSB was not designed with those considerations. I think that with those concerns as a constraint you

I understand your concerns regarding metadata aggregation. SSB was not designed with those considerations. I think that with those concerns as a constraint you kinda need a different protocol. I think that rooms2 required a new protocol because of the handshake required for two peers to connect. I'm not an expert on protocol stuff, I write one of the clients but I'm usually working on higher levels than protocol work. I suspect that rooms2 is not just NAT breakage but it has some of the handshake and security involved in it. If you want to dig deeper, I suggest asking for links on their rooms 2.0 repo. I'm not aware of a review like that, but I'm usually working with other stuff. I know there were some papers published recently, maybe those will appeal to you. :-)