For the use group meeting this Thu, HTRC has proposed solutions to the pull-down volume issue as a basis for user group discussion. The wireframe can be found on the community Wiki 
It has proposed interface for reminding users of pull-down volumes in the workset, removing such volumes and updating workset and so on.
You are also welcome to respond to this thread with your comments on the proposed solution. Thanks for your input.
Dear Scholars,We are having our monthly user group teleconference Wed, 4/24 3:30-4:30pm ET (or 2:30-3:30pm CT).The topic is: handling invalid volume IDs in HTRC workset due to takedowns.HTRC takes down volumes from the data store periodically based on takedown request from HathiTrust, usually due to copyright reason. Therefore it causes the work set inconsistent issue: if you have such a volume (which have been taken down from HTRC data store), but the volume ID is still in your work set. One side effect is when you perform algorithms on the work set, they won't perform on the taken down volume. So we are asking for inputs from the user community about ways of notifying users about the take-downs and handling this inconsistency issue.