On my current project I needed a solution as described above. So I did a search and found this thread.
Following the suggestions here I was able to implement this in about 3 minutes. Not only just delete the old image though, but to delete the image that was in a dynamically created and named folder.
By applying the behaviour twice, I was also able to delete the thumbnail as well (in a seperate dynamically created and named folder).
Well done WA on this extension that has so many hidden depths.