Joe,
I shoot with a full frame body (Nikon) and sometimes use the crop mode which cuts my frame resolution. BUT If I further crop the file in PM - not looking that it's already a smaller file - I may crop below a good quality print file size. Could PM offer a warning if the crop would make a file size below X - where I can set X?
What do you mean by "file size below X"? Pixels? Actual byte size of the file?
If the image includes areas you don't want printed, how does that make a better print size? You'll still see the unwanted elements in your print.
I'm not sure how useful this would be to anyone else. Photoshop, to my knowledge, does not offer such a feature and Photoshop is far more focused on printing than Photo Mechanic is.
-Kirk