That is right

That is exactly what I propose, do not create anything new, on the contrary, shut down two of the chatrooms and keep only one, it saves resources and it allows members from different sites to interact, and all of this while keeping all three sites independent, it should free staff time too. I rather propose it in public for others to give input in case I am missing something, as you said the hard part is convincing the administrators of all sites not just one.