They cant do nothing on Android if you dont use the play store.
Discussion
I didn't write anything different
anyways, until we use the Google services they might implement more aggressive policies in the future, such as uninstall "not-approved" applications no matter how they were installed
How they do that? Stealing out phones to uninstall apps?
Google services have root privileges on the phone. Google could implement such a system with 0 effort, the same way Amazon deleted books from users Kindle.