Am I far off in thinking that the core challenge would be replicating the transition between sub-groups? That moment where you'd like to move on from a conversation and can gracefully step away without interrupting a conversation to announce your exit, walk through the room until you hear something interesting, sidle on up to another conversation without it feeling obtrusive, then join in.
I wonder if the abrupt nature of popping into someone's conversation with a new video-chat window would go against this. Either way, seems like an interesting puzzle to solve. Plus, the market is big, has a ton of attention right now, and any product has some inherent virality built in since some number of attendees will try it again afterwards. Very cool.