Hello Tim
I begin by accepting that you mean no discredit with your mention of the aftermarket repairers and their connection with criminality. And begin by accepting that you will never eradicate crime from vehicle repair. Sophisticated criminals obtain as much information from manufactures and dealerships as they undoubtedly do from the aftermarket. Your key focus should be how to reduce it to a minimum and promptly catch those responsible and punish with sufficient deterrent.
The answer lies within the technology itself proving a legitimate business with no criminal involvement is futile, however access in vehicle systems and data is now a procedure which involves the use of secure internet IP addresses were access codes and software are obtained. Manufactures of key diagnostic tools and the end users should form part of a secure internet data base instantly cross referencing the electronic identity of both the vehicle and critical security components during the process of coding and programming. This secure data base can have a monitoring or flagging system with interested parties Police Government security agencies, Insurance industry and the DVLA. By instantly cross referencing this data in real time and by that I mean when an end user logs on his unique IP address, with perhaps a vehicle which has a default flag set against it , it should be possible to catch such individuals , know there exact location. To answer your question about registration there are in effect quite a few genuine expert companies currently operating at this level, most of them are known through professional industry bodies and equipment manufactures.
Hope these ideas are of some use.
Regards
Frank