Replied in thread
Having a #MUC open when certain admins are around and closed for new/untrusted accounts when not, sounds like a good idea, indeed!
It does not even need an #XMPP extension — this can be done by a bot, that runs on behalf of an admin.
Probably it is pretty easy e.g. with #slixmpp (#Python), but somebody™ (= not me!) has to write it — and convince the respective room admins of its usefulness 
Next week, we have an XMPP sprint in #Berlin. Maybe someone is up to the task?
