@alex @realcaseyrollins +100500
It's not possible to install 3rdparty apps on iOS without losing warranty.
Autoupdating is not usually straightforward. You still have to write the autoupdating code, put it somewhere and rely on some kind of service which will answer is there any update.
Not having your app in popular application market is means losing probably 90% of possible audience. Xash3D FWGS wouldn't have a two millions download if it wasn't Google Play. We tried, it didn't worked.
Getting published in alternative markets doesn't really change anything. Let's be honest, no one care about F-Droid except tech geeks. Did you heard that Amazon have their own Android apps market? No one, except those who own their book readers.
Also, markets have their own rules and they are often too strict. I don't know about the Apple AppStore because I didn't published anything there but Google Play is complete trash. Publishing something to Google Play may take the day of your free time just because you have to:
1) Generate screenshots for phones and tables and on different languages if possible. Missing it means that your app will not be shown in search results or it will not be first.
2) Write the description and translate it if possible otherwise you'll stuck with poorly made Google Translate.
3) Make sure your app is targetting Android 8 because Google really wants to drop the legacy Android versions and don't ask if you want to do the same.
4) Make sure your app have 64-bit compatibility. For most developers it's not a big problem but for Xash3D FWGS it was because the 3rdparty mods that are compiled only for 32-bit.
And that's not the end. They've recently added a new format of distributing apps which will allow Google to generate APKs on their side and remove unused assets or libraries. Sounds great? No. Because you have to show them your private certificate, the only way to identify developer. I hope Google secured them enough.
Does this really help Google to avoid poorly made applications filled with ads and probably violating somebody's copyrights to be published on their market? No.