Would you favor stopping low-dose aspirin and continuing OAC alone in a patient with atrial fibrillation and mild coronary artery calcification seen on routine chest imaging?  

Absolutely, most of the patients that I would treat with dual-antithrombotics (as opposed to dual antiplatelet plus/minus anticoagulant), have had clinical events. Most commonly MI and/ or stent plus atrial fibrillation. Your patient has one clinical event (AF) and another "subclinical" condition.

You could go a step further and ask if you would be comfortable stopping low-dose aspirin in patients with mild coronary calcification alone. Prior guidelines recommended aspirin above 300 Angstrom units on "ca scoring". This was lowered to 100 currently.