Apple can still provide all of the OEM features if they really want, the obvious solution here is to give people the option to install third-party things (eg. Please enter your PIN number to confirm a third-party installation) and then boom! You're finished.

It's quite obvious that the only reason Apple hasn't added that feature is because they have no intention on losing their stranglehold on the App Store. Without sole propriety of software, Apple's value proposition starts to crumble. So, why should we let them keep it? What do we, as a society, gain from letting Apple be the richest company in the world? The answer is nothing, and eventually some day when they go under we'll come to the realization that it was all a zero-sum game anyways.