> the company may not in fact implement any such update to their systems for years to come, given how rarely commercial airplanes are redesigned.

Boeing commercial airplanes are constantly updated. As long as the airplane is in service, Boeing retains a team of engineers that update parts as needed. If FAA review is needed, this will of course take longer.

BTW, anyone with access to the internals of an airplane could potentially sabotage it. Sadly, all people with access need to undergo a security check.