Great idea! Wish I would have thought of this before I went through my upgrade. You will still need to update the calibrations, as I believe that the factory defaults are what would be supplied.
Steps would be to build stock, Calibrate (be sure to have a dummy load), replace Nano, load stock firmware, calibrate with same process, then download the CEC firmware.
That is the good thing about this site, you can always pick up tricks and improvements from the host of people on it.