For ProjectSuite variables (and Project variables), right now these are clubbed into the main PJS and MDS files. This is making life difficult when different people have to change them simultaneously - and especially when using Source Control (SVN etc.) and when you have conflicts.
Also it is much easier to manage and less prone to error if these are kept as a separate file.
However, the file has to be linked to the main file so that the test scripts work.