Regenerate featured images after editing without plugin

Does anyone know of a way to have the featured image automatically regenerate after a user scales or crops it using the ‘edit image’ feature? I need to be able to simplify this action so that the user can regenerate the image while still on the post/page edit admin page.

When editing in post images, it appears that the image is either regenerated or recreated on editing. This is not the case with the featured image or images created using add_image_size().

Any help is appreciated! Thanks very much.