Has anyone acted as an MLO yet? If not, the number is not required. If the application is only taken and no terms have been offered or negotiated, then I wouldn't worry about the NMLS id number yet. Add to your procedures that once the application is assigned to an MLO, the number will be disclosed to the applicant by the MLO.
I can't herd the cats anymore, so I just set up the electric fences and let them fry when they stray out of bounds.