That's in a sense what Debian is doing with its experimental/unstable/testing/stable repositories. We also adopted a similar approach in build2 where we have qu

That's in a sense what Debian is doing with its experimental/unstable/testing/stable repositories. We also adopted a similar approach in build2 where we have queue/testing/stable sections of the repository. A newly submitted package version first lands in the queue where it is not yet visible to anyone. After it has been tested and reviewed, it is migrated to testing where it becomes available for testing by the larger community. After some time, if no issues are found in the package, it is migrated to stable. You as a user of build2 have a choice from which section(s) of the repository you want your dependencies.