One thing to mention here is that the specific IETF policy could work. I apologize for not reading the source document before commenting on the representations of it on this list.
The key point in that policy are the exceptions. In practise the IETF 'do-not-photograph' lanyard/label, as stated, only applies to small groups (like under 5 people). As soon as there are more people than that in a photo, the policy no longer applies. And it also does not apply to video coverage.
That would be workable, but unless that is clearly and specifically explained to people choosing this option it could lead to more conflict because of people expecticting the lanyard color to be obeyed in all circumstances. This could be seen as a bit of false advertising, unless it is very, very clearly expressed to everyone concerned.