Currently, attempting to install systemd causes dependencies that are not available in the portage tree to be pulled. Is it possible to unmask/add these dependencies for the (very few) users who wish to install systemd?
Could adding the systemd USE flag "unlock" the requirements to migrate to systemd?

I understand systemd is not much liked, but there are some few instances where it's necessary, like when attempting to install GNOME 3.8.

Also, my understanding of an operating system is that one should be able to install whatever package exists, and not restrict users to the "recommended" installation, but with systemd uninstallable, this is not the case.