There are already two radial menus in the vocalizer for calling out special infected: "Enemies" and "Warnings". And it's not possible to bind a vocalize command directly to key - you have to use a radial or client menu. Long time ago (and in L4D1) it was possible, but not anymore.

Regarding voice lines in Versus, you should know by now that all add-ons are disabled there (and in all other competitive game modes in fact). But I wrote a guide on how to enable vocalizer for Versus on official Valve servers, so you can check that out. For your local server, you can easily edit addonconfig.cfg and enable add-ons for Versus.