Would be great if there was an option to use Image CDNs, so that image requests were to the exact size image.

Thumbor is open source and recommended by Google: 

https://web.dev/install-thumbor/

http://thumbor.org/

 

Then there's also:

https://cloudinary.com/

https://www.imgix.com/

https://www.cloudimage.io

We are intereset on that too!