>I imagine official support for 3rd party app stores might open up some options for easily installing apps

Given you own the OS, that's not an issue. You can make it pre-jailbroken and load whatever third party app store if you want. The bigger issue is that no app store = no "normie" apps like uber or google maps. I suspect most of the stock apps won't work either because they enforce device attestation on the backend endpoints, so it'll be miserable to use. Note in the maps screenshot, there's nothing behind the modal. It's just blank, suggesting it can't load the map tiles. You'd be better off using an android skinned as ios (possibly vibedcoded) than using this mess.