Isn't that just what they already do? Apple has consistently framed the parts pairing as being about theft deterrence. I don't believe them for a second (and nor should anyone), but that is certainly what they claim.
I don't doubt at all that they see the theft deterrence as a significant benefit. I wouldn't even doubt that internally they justify many of their actions based on theft deterrence.
However, if it was only about theft deterrence, I would expect to see some things be a little bit different. If they actually supported customers repairing their devices, or third-party stores, there would be differences in how they approach this. We have plenty of history of Apple's behavior to know how they feel about self-repair and third-party stores, without even considering the theft deterrent actions.
How utterly and incredibly serendipitous for Apple, that they are able to solve the problem of theft, and it just so happens to also accomplish a ton of their other goals that they have been working on for a long time!
The problem with most of the theories about Apple having ulterior motives about parts pairing is that there’s no evidence that parts sales are even a blip on their revenue, not to mention a profit center. I have trouble imagining what those motives might be besides securing devices and restricting use of black market parts.
What is it about Apple that makes you trust them so much? Is it so hard to believe that a company formed around a ruthless businessman would continue to be ruthless? Or why would you believe that after Jobs died they suddenly changed?
The only serious potential issue I see with all of these restrictions is if they make 3rd party repairs too cumbersome or cost prohibitive. If not, then I see no downside, other than losing the ability to use cheap but sketchy replacement parts.