I already added a similar feature-request/-suggestion to the "User Community Feedback - Forum":
https://ciscocollabcustomer.ideas.aha.io/ideas/WXCUST-I-497
By issuing individual passwords to each particpant, it should be possible for Cisco to implement a feature to recognize and subsequently block multiple logins which use the same participant-password.
You may either vote for my feature-request (link above) or post your own.