Rather than a light, every camera should have a lens cover. Some opaque object easy to slide in and out of place. A tiny piece of circular plastic would do. Along with the light which, as you mentioned, should be required to be hard-wired with the camera connection so that the camera cannot work without the light, perhaps the little sliding piece of plastic could work as an on/off switch.

Imagine if every laptop & phone (and now, television) had one of these?

Heck, right now I have countless electronic eyes staring at me ... television, laptop, phones that happen to be in the room. Can I be sure that nobody's watching me remotely? Hell no.