I had a pseudo-plan for something like this but for reasons related to privacy I had two types of chatrooms:

* regular chats, existing only on the server, no leaking the chat transcript except via users, but never via server to server.

* chambers: a global chatroom, located at a server, maybe with a MQTT anyone could subscribe to.

This never left the early planning stages though, but I thought the segregation between federated chatrooms and regular chatrooms was of interest to keep in sync with IRC open but closed nature of chats.