You quoted me, so I'll answer. Though I'm not sure you're addressing the implementation that I was discussing with ken (K).
If this feature is implemented it should have an "owner's switch" toWhy would you want to turn it off?
What I suggested makes no changes to how messages are handled by email, nor any changes in how they are presented on the web site. It changes only a detail of how attachments and images (inline or attached) are stored. And in particular it potentially reduces the group's storage charges, which seems only a benefit.
As such, what I suggested differs in that significant respect from what Donald (the OP) suggested; but it solves the same problem (excess storage charges due to duplicate images), removing the need for moderator busy-work.