For obvious reasons, files already published on GroupShare cannot be deleted (you would only delete the files on the server, not on the clients, and you don't know which client has it already in his project list).
It would be great to have the possibility to mark these files with a status (or something similar), so that everybody knows that these files are "old". Our actual workaround is to assign this file to a fictive user (Old Version). But it is not really efficient.
In addition, after having marked the file as deleted, a message should appear on the client where this file is in its project lists, that the file is no longer valid.