Totally understand about the MBSSID incrementation. Just odd that they change the OUI after the base BSSID.
But yes, forgot to add that you CAN modify an existing OUI.txt file and try to import that into the system. (instead of an Internet fetch of the current file). I guess it just depends on how these OUI's are being implemented.
If it's random, then you''ll constantly be updating that file to no end.
If they just simply have some small set of custom OUI's that they stick with, then that's totally manageable, if you want to maintain your own custom OUI.txt file.