A tool that would be VERY helpful for contractors and subcontractors is one that allows the architect to save the drawings in various states of completion (design development, bid, construction,delta 1,as-built, etc.) and then allows for a quick and easy comparison between these various stages. Perhaps a tool that has a different color for the old and new drawings so that when overlaid, it is easy to see what has been removed and what has been added; this is similar to the comparison tool that the Etakeoff program has (I am in no way affiliated with this company - I work for a general contractor).