I believe that we all, as users and developers, should have an option to choose where and how we can buy, install and distribute software.
Whereas today it is not that obvious because using smartphones users are somewhat obligated to use official interfaces like App Store or Google Play, in my opinion, the place where we do this (install, buy and distribute) not only should enable us to make the choice. The place should also encourage us to make it.
In my opinion, already existing solutions where we can search for an inspiration are protocols - for example email or web ones. Using any operating system, mobile or desktop, we are not forced to use any particular interface - neither a particular internet browser nor a specific email service - to make a use of the amazing technologies. We are free to choose Safari or Google Chrome to browse the Web and free to choose Gmail, Apple Mail or Hey for sending emails. In my opinion, this is the power of ultimate solutions - they are not associated with any specific company, they are general and their only purpose is to serve people, not to make an income.
Hence, exactly like today the app stores gathers all options (applications) for browsing the Web (internet browsers) and sending emails (email services), a general platform with software should gather all options (app stores) for installing, buying and distributing apps, giving all us as a choice of where we can do these activities, aggregating all the options on a single platform.