Is it possible to put the entire Teams environment in read-only mode?

We are in the process of planning out a tenant to tenant migration. We have a couple thousand teams, but only want to migrate over the most recently active teams. I would like to put the old teams environment in read-only mode so that after our initial migration, people will have some time to go back and see their old teams, but not make any updates to them. Is there a way to do this easily? As far as I can tell, there isn't a switch or something to do this. My initial thoughts are:

• Update the Calling policy to disable calls
• Update the Chat policy to disable chats
• Move all Owners to Members
• Enable channel moderation so only owners can post chat messages
• Update SharePoint permissions so that everyone has read access only

Any feedback is appreciated. Thanks!