I see it as less practical mainly due to the extant tooling and age/maturity of the project.

The ways that I'm most familiar with are use of software like Artifactory - basically a multi-repo. Using such a tool, any package or artifact can be readily retained for future use. Then, for builds, one only needs to ensure that it is used as the package source, regardless of type (PyPy, Docker image, binary, RPM, etc).

Alternatively, one can use individual repos for any relevant package type but that's a bit more overhead to manage.