I'd rather penalize the application than the technique. Windows was rumored to long have "quirks" that would do better things for apps that had bugs that the OS ended up fixing instead of the app.

Javascript systems have long had polyfills for varied browser feature comparability gaps.

Whether you agree with these, making probing detection via fingerprinting illegal would take away this lever. Making surreptitious tracking via fingerprinting illegal? Even for state actors?

Yeah, that's probably reasonable. If someone is going to wear a tracking collar in exchange for "free" services, a little disclosure makes sense.

Yeah, the problem is how the data is kept and abused afterwards.