There is flexibility in FAA projects....

When the FAA comes out with Service Bulletins, Airworthiness Directives, Suspected Unapproved Parts Notices, or other mandatory requirements for safety reasons they do  it because they have found a need to alert operators and owners of aircraft and rotorcraft of bad maintenance practices, fraud, or just a problem that the OEMs didnt foresee. One good thing is that the FAA does have some flexibility sometimes in that they have something called Alternate Means or Method of Compliance. That means that an operator or owner that they are willing to accept another means of showing compliance to resolve a safety issue. Each have differing requirements to demonstrate compliance but it is entirely possible to achieve a variance.