ha, so you don't mean having multiple distros dropping their "base systems" and only providing the "addon" part in their repos, but actually having the "core" distro include all the "addon" flavors into their repo. haha really, really "simple".
"Hey debian, I'm a one man operation out from North Korea, and I made this customization package. I swear it complies with every privacy and security policies, and that it is compatible with your core system. No it won't break anything. Can you please include it in your repo?"