It makes sense, I think. OBS control, model expressions & toggles, Stream Deck mappings & events, audio mixing and control, HDMI matrix routing, even things like scraping YT sub count, stream control, and the YT chat feed. All those map quite nicely to the MQTT data/message model.
And mosquitto already has a WebSocket listener, so I don't need to write a backend at all. No database, no backend. Just various scripts and glue layers, and a web frontend, all talking to the MQTT server I already have running anyway.
It also solves the HA integration issue, because I have stuff (like putting machines/monitors to sleep when we hit the light switch in the office) that HA needs to handle, but also streaming is involved (disabling that during a stream to avoid accidents). If everything is in MQTT it's easy...