I would like to request a feature to easily remove outdated image sizes without having to regenerate the thumbnails.

My situation is that I have a library of 32,000+ images, each image currently has up to 11 different thumbnail sizes. I have reduced the thumbnail sizes to 7, so four thumbnail sizes need to be deleted.

I would like to see a new parameter wp media regenerate --only-deleting added to simply delete all thumbnail sizes that are no longer needed. I know that wp media regenerate also does the job, but it also regenerates the already existing thumbnail files, which is not necessary in this case.

Hope my request makes sence for you. Thank you for all the work and time you put into wp-cli!