I fully understand the desire to keep using the M9, M9P, and M Monochrom. They produce images like no other camera. I've used my M9 for over 10 years, see no reason to replace it.
If this problem can be solved by "just typing", after all writing Code is Just Typing, I'm happy to help. Plus my wife pointed out that I am geeking out over this. Too Much Fun.
The calibration code reads the Sn from the DNG file, creates a calibration file using the serial number if verified in both locations in the DNG file. Now all I need to do is have the correction program read the SN from the DNG file being corrected and use it to open the proper calibration file. The user will need to store the cal files in a subdirectory, like "C:\M9CAL".