Removing assigned developer license based on inactivity

I have a customer who has a large set of assigned licenses and is not interested in converting them to floating licenses due to special cost circumstances. However, they are having difficulty managing their assigned licenses and making sure people who aren't using their license any more have their license revoked.

I have found a way to remove/add a license to a user using the API, but I am having difficulty trying to determine who to remove a license from.

I am looking for a way to determine if a user is no longer needing a license. As well, I cannot modify the Jazz server code.

Ideas:
1. Using a query or API call (no clue how to write one that covers all possibilities)
2. Putting a trace on WAS on com.ibm.ws.security.server.lm.ltpaLoginModule=all (very, very noisy)
3. Running a trace on the ldap to just check who is logging into RTC
Suggestions?

Related work items:
https://jazz.net/jazz/web/projects/Jazz%20Foundation#action=com.ibm.team.workitem.viewWorkItem&id=38904
https://jazz.net/jazz/web/projects/Jazz%20Foundation#action=com.ibm.team.workitem.viewWorkItem&id=95814