[rachofsunshine]

In particular it's "noncommutative" - I want to check English before I uncheck French.

I tend to agree with other commenters here that it's better to just make a checkbox list and require one to be selected. Or in cases like language, maybe have a primary radio (mandatory) and a secondary checkbox (optional) section, where you need to select a language for the app to show you thinks in but can indicate interest in other languages' content.