My initial thought is that these kind of edits should be rejected. All content uploaded to Stack Exchange is automatically CC-BY-SA licensed, and this is often incompatible with the licensing of the source image. In the example noted above, the original is GFDL licensed, which is incompatible with CC-BY.
Obviously, this issue doesn't exist for source images which are already available under CC-BY-SA or a compatible license, but I suspect that's a minority of these edits.