Step One:
Put chip burning chip detectors to adequately monitor the gearbox and link it to pilot caution warning system. You do not need a $500K HUMS to do this. Let the crew either command a burn (Bell 222 technology from the 70's) or automate it with a CAS message alerting the crew. Multiple successful burns should be indication of bad things and prompt immediate crew actions. Unsuccessful burns should have the same result.
Step Two:
Implement step one as part of the regs (i.e. do step 1)
From the L2 design chips may have been accumulating on a HUMS read mag plug (not annunciated) which if annunciated could have given this crew actionable information.
The Sultan