Wonderful post, and I love the point you make that by taking away the female leads, the emotional and moral core of their world has been sucked out, leaving a hollow shell. I remember reading Macha's discussion of these episodes over on http://www.teaattheford.net/, and how the images of shells were everywhere.
Interesting thought, that the reason Wesley would say he loved Fred before he knew her was that he was really in love with the mythos of the madonna-whore; his version of Fred was the shell he filled with that mythic ideation, the perfect woman.