(as we have discussed with Matt) It would be nice to distinguish stages properly. Something like: stage3-${arch}-openrc-${date}.tar.xz Would probably work. So applies to the stage4 archives.
Seems like a fine idea to me. I guess it would be nice to keep the files available using the old name as well for some period of time. Maybe we can hardlink them if the mirroring infrastructure supports that, which I think it does. I think we just need to update the spec templates in releng.git and manually add another stage3-*-openrc-latest.tar.xz symlink.
