IMHO, the best I’d seen of mouseless UI was the pentadactyl/vimium/vimperator model (possibly originating with (lynx or elinks somehow) where a hot key was pressed and everything clickable was overlayed with a number allowing a direct click. Obviously simpler than what is being proposed here, but it was my preferred way of using the browser for some time.

Tridactyl is alive and kicking for Firefox today?