What if a genuine part is modified. I am not sure it is a solvable problem?
> First they are indeed not exclusive options, locking parts when the phone is locked is a possible option.
If that is technically possible I am all for it (but if I had to choose between no integrity protection and integrity protection that makes it harder to repair, I don't know what I would choose). However if you are a phone, how would you distinguish between a legitimate repair and malicious swapping out of parts? Sounds like incompleteness theorem would say you can't