Yes that's an important point. The overlay is an asset - a huge one at that.
Dunno, never heard of anybody using Sabayon (which is stage 4 gentoo +
custom overlays + binary pkg manager + a lot of useless things and ideas
like the pkg manager guessing your needs and when you should watch porn) for
audio. Even I myself used it on a laptop and had Gentoo on a desktop for
DAW. That was some 2-3 years ago. But well, if just one person builds and
hosts binaries, it might be a solution ey?