Option to either save entire frame or cropped region

We have the option to render a region, and also an option to crop the render to the region limits.

I would like to add an option in Render Window or Compositor node that allows you to save a render region cropped.

Sometimes is useful to have it render with the whole transparent surroundings but you never know, sometimes small render regions are not worth keeping the whole thing, so in the moment of saving, an option saying "crop render to limits" would be very useful