I agree with Howard; if you don't number the machine then you don't change the process.
However, I also agree with Marc, if the registrar is "bullheaded" he can make life miserable for you.
Best advice "call your Customer"
On the other hand, IMHO the PPAP/ISIR is the best method available for documenting the quality of the product/process. I would suggest updating the PPAP for every change.