I think currently your best option is to set up your array of source sizes and then loop through that array to render your srcset using crop on the original image. The height can be calculated from the ratio between width and height.
I’d probably create a custom method that adapts the srcset method for cropped images, i.e. using
crop() instead of
Mid priority doesn’t mean it can’t land in 3.2, it’s all still pretty much in flux. However, the reason that it is only
mid priority is probably that the missing options are not really a show-stopper but rather “nice to have”.