I guess more simply: print a step wedge and pick a landmark on the wedge, then reverse the wedge so that the chosen landmark prints as the reciprocal value i.e. paper white prints as full black OR the last step showing density before paper white prints to the last step showing separation before full black. Right?
If I understand your original question correctly, you will want to match both the dark and light ends of the scale, not just the dark one. The major difficulty in making copy prints (positive/negative/positive) is in controlling not the density but the contrast. It is very easy to get excessive contrast from printing paper, which is one reason why in-camera paper negatives are often pre-flashed.
It seems that you would want to print a step wedge and adjust both the exposure and processing until the last step before maximum black, and the last one before paper base white, have their reciprocal values after the reversal. The steps in between may not be linearly related to the corresponding densities on the original, so there may be some tweaking required for "best" appearance, but at least you will be starting with a full-range image.