Node already has tools like audit that tell you if there's problems of various kinds with your packages. (The quality of audit, and NPM in general, is pretty poor, but this could apply to many package managers, NPM is just the current example.)
So sure, allow people to pull their packages. But require a 60-day "cooldown" period where the package is still available and comes with a warning every time it's downloaded that on such and such a date it will be deleted, by request of its creator. The note could include a message from the creator and links to viable replacements.
Also, assuming licenses permit, do NOT delete any existing copies of the package or break when the user tries to update again later. Just keep sending warnings until the cached package is removed.
Finally, make it clear to authors of packages that if they submit to NPM, this is what will happen if they choose to remove their package.
What would be wrong with such an approach?