Now that most CAD systems recognize and honor geographic coordinate systems, I think its time to embrace the use of real world coordinates for all design work. For those who don't like that approach, it is possible to set up Auxiliary Coordinate Systems for areas where local or relative coordinate systems are wanted or needed.
The only other alternative would be to setup a custom geographic coordinate system. I've done this for one client that insists on using its local, city-wide coordinate system instead of State Plane. This did not take too long, but doing it for every structure on a project would seem extravagant.
Another option would be to setup a Home model in every file that uses true coordinates and reference in the model with its relative coordinates. Once moved, rotated and possibly scaled into its real world location, anyone needing to reference in the local coordinate models would attach the Home model with live nesting.
Seems like more work than requiring the use of real world coordinates.