How about an option to show the full “path” of a document in the header. It would be useful for situations where you linked to a file from some other document, and wish to know where it is without opening up sections of the Binder.
The trouble with that is that the header is a way of renaming your document. You can click in it and change the title - useful if neither the binder or inspector are visible. The “Reveal in binder” feature is intended for this purpose. Yes, I know it means you have to click a disclosure triangle if you want to close that section again. 
So, this one is a negative for the foreseeable future.