some packages explicitly depend on metacity which seem to work with expocity. Can there be a virtual or either/or dependencies to avoid package blocking. I have found 2 packages (gnome-python-desktop and gedit) that behave this way.
http://www.pycage.de/software_expocity.html if thats the homepage and its last release was really 2004, we won't be doing this. please re-open if that is not the case.