Guix has a different take on this problem: it provides package transformations to modify the build graph on the command line (or in a Scheme file), which don't

Guix has a different take on this problem: it provides package transformations to modify the build graph on the command line (or in a Scheme file), which don't preclude the use of binary substitutes and reproducible builds. All stuff is cached in /gnu/store so people won't have to rebuild packages, and with `guix publish` people can share built binaries with others (discovery via Avahi optional).