I wouldn't mind if you could buy parts from anywhere, but Apple would deny use of parts that were reported stolen. That way you keep a fair and open market for parts but also clamp down on theft. If repair shops are picking up stolen merch, that needs to stop, but there also needs to be general availability of parts at fair prices - and it should be possible for me to kitbash two of my own devices together into one working device if they're broken in different ways.
Who decides what a fair price is? That is the challenge that would never get reconciled.
Server side validation of parts aren’t new. My BMW has a fair number of parts that the car will not accept unless they contain an encrypted validation file from BMW AG in Germany. So pulling the part off a car in a junkyard or a third party isn’t going to work.
BMW doesn’t sell their parts at what I assume you call a “fair price”. My right headlight is an LED based light that BMW charges $7K for if one of the LEDs die out. And it is one of those parts that need to be “coded” when replaced.
And cars are the poster child of right to repair due to strong laws and parts networks in place.