I love the Export tool, but I find myself wanting to do a quick crop after resizing the image. There are some pictures where I work quite a bit on the framing and others where I quickly correct WB and exposure and want to export a set of 6x4 jpegs ready to upload to a print website. The current options in the Image Sizing section of the Export tool do not allow me to do this in one step.
It's a big deal because it would mean for casual, aspect ratio specific use such as name above one wouldn't have to either keep track of said changes as virtual copies or remember to undo the specific, and in my case temporary, crop that is required to get the desired aspect ratio. It's not a big deal, just one more potential export option that could be nice to have.
Maybe I am missing the point here but it sure seems simpler to crop first. As Lee Jay pointed out you can crop many in QD Panel. Export. Then [Ctrl][CMD] Z to get back to your original crop-on many images. That sure seems quicker to me than this. More control-less fiddling.