Yeah, I know the appeal, I have used Gentoo before, but now I only customize the programs that I actually want to customize. You can do that on Arch by using "asp checkout packagename" to get the PKGBUILD, and then you can change it and build (though I have had problems with that before, like in the case of Emacs, with the package's authentication, it wouldn't build even without customizing). But it's a rolling release distribution, and Arch isn't really built for that, so I don't know. But with the ports collection in any BSD (or Crux, I guess), you can get a lot of the benefits of using Gentoo as well, and at least on OpenBSD, their Makefiles are very clean and easy to modify. You can also automatically patch things with it.