Ratio Crop

How easy would it be to be able to specify just a ratio crop?

I’m using this plugin the the aq_resizer script which I use to create multiple image sizes to fill the srcset of my image. Ideally I’d want the user to upload an image at a minimum size with the correct ratio but have the option of uploading a double size image for hi-res screens.

Currently I can only set a fixed size for the crop, so I have to choose whether to set it to the 1x image dimenions of the 2x image dimensions for hi-res, which removes the ability to make uploading 2x images optional..

..If I could just specify an image ratio in the admin, then this plugin would crop the uploaded image to the correct ratio, then aq_resizer could handle resizing that image down to the required sizes, 1x and 2x.