This is basically what I want, most of the time, and it's hard to achieve it outside the App Store.
IIRC Chrome even asks you if you want to enable that setting once you download an APK file.
>Workstations need to be totally user-controlled,
I believe chromeOS is a good example of a stripped down less tunable OS that works great and is perfect for inexpensive Atom based machines that still have good build quality, battery life, and displays while being simple to use.
I believe trying to push the "store" model to desktops smacks of a solution that generates a lot of $$$ for M$ and Apple in search of a problem.
The problem with that is that the nature of the issue is that it doesn't matter to you ... until it does. Like freedom of speech - you will never notice that your government is censoring you until you have a controversial viewpoint. And then it will matter. But all the people without those viewpoints will still wander around saying they can't see what all the fuss is about freedom of speech. This is intrinsically a problem you have to care about in advance of when you need it.
Phones are more then likely the workstations of the future (when we figure out how to use them more effectively then the workstations).
And why this extreme generalization, exactly? Don't you suppose you could have privacy, security, and perhaps even simplicity and ease-of-use with a totally free and open phone that grants control to the user? You really don't explain how "a totally open platform" is mutually exclusive, nor how your own personal needs require the inverse of freedom. Further, the distinction between computer and mobile device are irrelevant given so many people depend on the later as their main computing device. They should be offered the same degree of control as someone with a computer has.
Ultimately, you cannot have privacy and security in a closed-source restricted platform, even if it's backed by good intentions. You're at the mercy of a few companies and as soon as they abandon the device, or make a mistake, you're exposed. And as a consumer, you're forced to buy into their ecosystem instead of having the choice to provide your own solutions. This is already true for the hardware, such as the black-box baseband required to connect to cellular networks.
While this kind of support doesn't technically preclude open-source code, it's hard to find both in one. Red Hat is one rare exception to this - providing a comprehensive, supported solution that also happens to be open-source. But the economics tend to push it to be one or the other. In this case, I'm perfectly fine making that trade.