That green ring sounds cool. Conference groups, where one tries to enter a group, but doesn't know anyone in it, are one the biggest challenges of a conference. If you could simulate open shoulders, closed shoulders, that would be a way to make this, better than reality. If everyone in a group has closed shoulders, it appears obvious they are not interested in anyone new joining. And also as in real life, a more welcoming group will stand slightly differently, but a newcomer can feel the difference. A slight opening of the shoulders in the group circle, allows one to enter, without feeling rude. Simulating that feeling, by making a switch, sign, or setting, may be a breakthrough? Very exciting program. Going to try soon.

I like the idea of having some sort of easy-to-see marking. The specific realization in terms of a green hat might be non-optimal, because green hats have an unfortunate symbolism in Chinese culture.