Have you checked out the possibilities with the "Delayed in state" option in State - Notification setup - in the Workflow?
It's not very customizable, but at least it gives you the opportunity to notify one or more employees and/or groups, when a file has stayed in a state for a given number of days, and will re-send that mail every given number of days. You must set this up on every state you need to track this.
This was a feature that shipped with EPDM 2013, so you need at least that version.
Hope this helps a little.
Best regards, Martin