As a subcontractor working with many different architect's projects we have to have multiple versions (4 typically) of Revit loaded.
Keeping track of which project is in which version (I cannot upgrade them as I would be very unpopular with the other collaborators!) is difficult and time consuming.
Revit obviously knows which version it is as it wont let you open a newer version and will upgrade an older one, could it instead offer you a choice so if it is from an older version than you currently have open it asks if you want to upgrade or open with the correct version OR if it is from a newer version it simply opens in the correct version?