Given the nature of software, I don't believe the OEM can prevent mishaps by locking down the software...
the OEM does have ulterior motives (possibly influenced by by EPA/CARB requirements/mandates);
locking out hotrodding/hacking efforts is of no consequence... if something is not right then the "software" won't work with the rest of the vehicle (due to both the complexity or the software, and the sanity-interlocks designed into it)... in fact the OEM's own software bugs will continue to be the OEM's worst enemy, not someone hacking the CAN/modules for the purpose running modified mechanical parts.