@ThomschUnfortunately a lot of the features you mentioned just aren't possible if the users don't have OneDrive & SharePoint licensing and access. They'd experience jarring failures when they need to directly send any files or present documents in private chats/meetings (needs OneDrive), and without SharePoint they wouldn't be able to do that in team channels or meetings either. OneNote users also require OneDrive since that handles storage and sharing of their notebooks. As for revoking the Team site's permissions, Teams expects associated team site and exchange mailbox permissions to match the standard permissions assigned when a Team is created. If they don't match then features within the Teams app and the connectors that integrate with it (Planner, Power Apps, Forms, Wiki, etc...) tend to break in unexpected ways. I've managed to break permissions on team sites a few times, the one upside was that a lot of people told me about it very quickly.


It's definitely a slog to evaluate the user experience, compliance risk, etc... implications of making a big move to cloud file storage, but I'd consider looking at the available controls and initially rolling out onedrive/sharepoint with heavy restrictions until you reach a higher comfort level and can allow things like external sharing or file downloads.