Hi Mike,
Adobe LightRoom has several tools to crop a file;
A: Straighten
B: 9 overlays - modes (see attached screenshot)
C: a palette of ratio's & custom one's. (see attached screenshot)

Those tools give me much more control over how/what to crop. [as photographer, I like to use other overlays then the boring 'rules of thirds'
So as for now, before printing with QU, I went over each file over, as last step, to Adobe LightRoom, to crop. btw It is also non-destructive.

Missing something? Or is it considering whether it is a desirable, to be developed, module on the page-editor tab. (or elsewhere)

With regards.