Hello,
I have been hearing the transition to AP for the last few years in some seminars regarding
FMEA.
In my actual company, Tier 2, none of the customers have required the implementation yet but in a previous company that I have work a customer ask for this evaluation even before the last version of FMEA handbook was released.
It would depend of how many new projects, how many customers make the transition and how often you review and update the FMEA that you will reach the point to change the FMEA evaluation for all the customers.
My recommendation is to follow your customer requeriments and have a template prepared with the new evaluation method and a Action Plan of implementation.
This way you will not get surprises and your answer to your customer will be agile.