vim ebuild doesnt install a link named vi perhaps this has already been argued about, but a lot of people expect vi to be installed, even if its really vim.
Not currently a good idea. There is the original vi in the portage tree and numerous clones. An ebuild shouldn't have to check to see if the other programs are installed, IMHO. Gentoo-Dev would be a great discussion area for this topic. BTW: Luke, I love the QT library :)