[throwaway189262]

> You can already authorize an arbitrary third party Android app to act as an app store

Apps installed with it cannot auto update without rooting your device. Rooting breaks many things (on purpose). Defeats much of reason for store vs side loading.

> and it would be completely compatible with everything in the Android ecosystem

Definitely not. You would never pass "safetynet" anti-root checks. An alarming number of Android apps no longer run on AOSP. Only on Android devices unaltered and locked at bootloader level. Google recently upgraded these root checks to be "unbreakable" by using TrustZone.

Android started out much more open, but big G is slowly choking it off. Having the core OS open source is pointless if nothing runs on it. And we're slowly getting there