I don't think that we want to add that by default. It will complexify the interface for everyone else.
If you reupload your images with FTP, it will overwrite the images in the upload folder. It should not be a problem for badges. They should just get the new version of the image.
Of course, their thumbnails need to be regenerated in order to see the new image for resized versions of the images, like for the products images and that can easily be done by just deleting completely the "thumbnails" folder in your images upload folder.