Kghostview is a ghostscript viewer and there is no need to pull in another ghostscript viewer like gv when one emerge a package that depend on "virtual/psviewer". I therefore propose to have the kghostview ebuild modified to include a line PROVIDE="virtual/psviewer"
see bug 127589
The "virtual/psviewer" is already in the portage. At least the gv ebuild is providing it. Packages like lyx has a dependency on it.