+1 for that. The
Quoth Map Paks basically work on that principle - the map plus all the resources are stored in a single pak file.
In order to make it work without engine support I wrote a batch file that renames the file to pak3.pak, but the idea that engine support could make the method slicker was something I had in mind. Dynamically swapping a map pack in/out would be nice, or just having a GUI to select the pak files.