While this would fix the above problem, two points remain:

1. This does not remove any tarballs.  It wouldn't be hard to do, but I
   am not sure if there would be any unintended side effects of doing
   so -- at least immediately.

2. There are functioning packages on NonGNU ELPA like haskell-mode that
   were also added to elpa-packages then removed, and still linger in
   the archive without being updated.  This would get rid of those too,
   which might not be a good idea.