I do not understand your reasoning. Any app store or in general any source from where an application could be installed implicitly provides a trust model. Whether it is Google's Play Store, a GitHub repository or e.g. John Doe's personal website. The users then have the freedom to choose whom they would like to trust.
> Has that "educating" and "targeted measures" ever worked?
Yes. Users are cautious before running anything as root. They check a browser addon before installing it. They do not open media from unsolicited e-mails. And so on.
It is, however, all besides the point.
Even if there currently were no effective targeted measures that could be used, it still would not mean that we should resort to undermining everyone's freedom, in my opinion. Not in this particular case.
There are legitimate cases where everyone's freedom is restricted in order to make the society a better place. For instance, we as a society have chosen to not tolerate stealing and we put the individuals who do so behind bars. This is broadly accepted because it brings benefits to everyone. We do not need to worry about being stolen from that much.
However, there is no general benefit to the society that I am able to see which would materialize as a result of limiting everyone's freedom to use their own devices. I can only see a lot of negatives.
Worse, there wont even be a vetted application. It will only be an unvetted application you'll be asked to sideload to get the functionality at all.
And soon: alternative app stores, with their own rules and no central control. From Adobe, Google, and so on.
>But it should be addressed by targeted measures against the offending applications and by educating the users
Has that "educating" and "targeted measures" ever worked?