At what expense/frequency, though? If it's just to cover the ocassional (unmodified) car that can't be made to report as "Ready and OK" per OBD2, it's just easier to use the existing repair exemptions process. (Spend a certain amount on repairs and get another cycle of inspection passage.)

If it's to cover modified cars, those are a trickier situation. It's easy for some to game the system so that it "passes" on the magic day and then fails the other 364 or 729 days in the cycle when it's actually being driven.

In either case, it seems like the expense of operating and staffing gas sensing stations, rolling road dynos, etc. Probably better to just turn a blind eye to that case as well.