I wish there was a way to do it without all the problems of having cameras on people's faces.
Just make it obvious that they're not ordinary glasses, but recording devices.
Not just a tiny LED that can be covered, but something like the camera is on an arm that swings out in front of the wearer so there's no mistaking that a recording is in progress.
The fact that they're designed for stealth shows the nefarious intent.
For AR glasses the current best option for tracking is inside out tracking so the camera would basically always be deployed.
I don't think we have to go so far as assigning nefarious intent here, there are a lot of reasons they're designed as they are. For example your proposed solution is bulky, expensive and prone to damage, so there's plenty of non-nefarious reasons they don't have it operate that way.
Just make it obvious that they're not ordinary glasses, but recording devices.
Not just a tiny LED that can be covered, but something like the camera is on an arm that swings out in front of the wearer so there's no mistaking that a recording is in progress.
The fact that they're designed for stealth shows the nefarious intent.