Back in the Bootstrap days, we used to have a script that we ran right before pushing to the releases directories that verified that all expected files for a release actually existed. bug 813757 is an example of a case where this would be useful. In the new world, this is something that could be run as part of check permissions I think. I think the script I'm thinking of is https://mxr.mozilla.org/mozilla/source/tools/release/bin/verify-locales.pl. I will r- any patch that uses this existing script, the useful parts of it should be ported to Python and there's probably a lot of things that could go in lib/python/release :).
We use beetmover with explicit list of files and it fails if something is missing.