In the years prior to your organization moving to G Suite, it was relatively common practice for users to create consumer Google accounts with their corporate email address (for example, to monitor Analytics, manage AdSense, and collaborate in Docs with other partners who were on G Suite.) You were able to address active employees' use of consumer accounts during the rollout, and you are now concerned about blocking former employees who could potentially still have access to those services even though they don't have access to their corporate email account.
What should you do?