So, I had this idea after looking at a post on the RPi forum not too long ago and now I figured why not a Gentoo-based Raspup? In fact, why stop there when we can also have a Gentoo-based Pup in general. Might take work and effort though I know.
This hyperlink is to the original RPi forum post btw.
Otherwise, I still hope for an update on the orginal Raspbian-based Raspup though. Just thought I'd provide an idea.