Changing Connect 8 to a read-only site

We are moving to Connect 9 and we want to turn our Connect 8 environment into a read-only site. We want to prevent people from creating new recordings. We can do that by removing people from the Authors, Meeting Hosts, and Training Manager groups. However, this only prevents new recording from being made. Anyone who was a meeting host in an old room can still go to that room and create a new recording. How do we prevent these meeting hosts in these old rooms from creating new recordings? Any way to bulk change permissions? I am open to suggestions.