I've calibrated my Aristo VCL variable contrast head using a step wedge. I chose the highlights (threshold) to standardize against. I found that for this head there is almost exactly a 10x exposure difference between the softest (all green light) and the hardest (all blue light) grades of Ilford MGIV FB/RC. By creating a table of exposure compensation factors for each quarter-grade in between, I can pretty much make any grade change in one-quarter increments and come very close to matching the correct exposure change on the first try. Usually a single test strip confirms the new exposure, if there is any doubt.
This is a great time saver to put me in the initial ballpark with a minimum of fuss. Fine adjustments at the new base contrast can then begin immediately. Saves time, saves paper, saves frustration.
I don't see why you couldn't do the same with a color head.