Think the "safe" way forward is to have the cases go the same way we do XForms, no real deletions, just rename the doc_type, to like CommCareCaseDeleted or something, and have the filter pick it up that way.

ES lets us also set "expirations" on certain docs, so if we relaly think something's deleted by the COmmCareCaseDeleted filter, then we just have the document disappear from ES after say 1 hr or something.