Let the user write relative paths on kfilewidget.
If you go to /foo/bar, and write on the file combo acme/file.txt, the kfilewidget will bring you to /foo/bar/acme, and then read file.txt.

This happens both when pressing Enter and when you accept the dialog by pressing OK.

I've doing some coding on this stuff (kfilewidget & kdiroperator), and this seriously needs some love.