I had some thoughts this evening and I think I have taken your spec and fleshed it out a bit more here: https://xena.greedo.xeserv.us/files/Project%20Register%202018-04-07.html. I welcome any and all feedback for this approach.
> It is of course possible to use HTTP access logs to see what APK files are being transferred, but this only shows installs - not uninstalls. Such a solution also doesn't show usage over time. (Is someone just trying out KDE and then throwing it away, or are they using it as their daily driver?)
I was gonna ask this question, and this is valid justification. I like it.