Firstly, you can’t simply move files on your server. (this is also a very server specific thing, depending on server type, it’s configuration, folder permissions etc.)
Secondly, image regeneration tools must “be aware” of the file paths changes to be able to proceed with the regeneration, that’s why you would not be able to use it.
Thirdly, images are not only files in WordPress – it’s an attachment post type, which data is stored in multiple places across database. I think that might be problematic as we’d need to store to paths to one image based on image size.
Believe me, there are much more questions.