I think this is a bit misleading to the point of disingenuous.
The NHTSA is not cracking down on the practice of putting non-TPMS wheels on a TPMS car; what they're doing is taking a harder look at those who put run-flat tires
without TPMS onto a TPMS car, and dictating that all cars equipped with run-flats are eqiupped with TPMS going forward.
The NHTSA is unable to stop you installing non-TPMS equipped tires
on your TPMS car; what they can do is if a run-flat tire without TPMS loses pressure and then fails (i.e. the sidewall gives out either because you're driving too fast or too far) causing any significant damage to your car or others then that would be grounds for a report to your insurance company that they may
use to deny a claim.
If you have non-run-flat tires
) on a TPMS equipped car, then it's reasonable and prudent to assume that you are well aware when your tire goes flat because the car handles like crap. It's no different than in a non-TPMS equipped car at that point.
The NHTSA is not a police force; they are an advisory body only. Even in the event you run run-flats without TPMS then it's actually quite unlikely that you're going to get yourself in particularly hot water because in order for an insurance claim to be denied it would have to be proved that the lack of TPMS caused the issue... i.e. you would have to have a sidewall of a run-flat fail hard and actually be unable to control the car. In either instance you're probably going too fast or shouldn't be driving anyway; I've had a run-flat fail hard (not a BMW) and the likelihood of you losing control is exactly the same as if you had a tire blow out.
No, I'm not an attorney but I am well familiar with the NHTSA and what they can and can't do.