This could be done in one of two ways:
First would be the ability to downgrade a users license from Full to Free Restricted when their account is deactivated. This will prevent users from being reactivated as a Full license. I think this method would just be a blankey functionality that when a user is deactivated, their license is updated to Free Restricted.
The second way this could be done is my adding another value in the UserType attribute in the SCIM provisioning capabilities. This would allow for us to upgrade/downgrade users without having to deactivate them.