Ha! Answering my own post: Here's where USERS should bitch and moan to software designers about the little UI things that trip one up:
There's a VERY easy way to crop using the existing AR, but it is hidden by BAD UI DESIGN. The button is "Front Image" in the Crop Tool options bar.
What this does is expand the crop marquees to the full size of the image, and keeps them in this AR as you size them. Fantastic! Just what I needed! BUT....
The button labelsucks. For all I know, Adobe has changed it since PS7, but in PS7 the label gives users very little hint as to the button's actual function. For one thing "Front"?? That implies there's a "Rear Image" somewhere (AFAIK, there isn't).
Anyway, if you consistently and politely call these little things to software producers' attention, we all get a better product and often you can get beta tester status. So send in those comments! Don't be shy! If it's an issue w/you, chances are it's an issue for somebody else, maybe thousands of users.
"Putting the HARM in 'harmonica' since 2005."