As Stephan mentioned in his mail, this path could be replaced by the path of the project file (he called it virtual root). Why? Just because I have more than one working directory. I have a development release and one or more branches / customer releases checked out. If the project file would use the virtual root, I would have only one project file to load.
I'm not sure I totally understand you, if the project file is in the vcs and the base path is relative to the project file why do you have to copy it?
Cheers Lex