In discussing the idea of the future of concerts where hundreds and eventually thousands of people attending, we are counting on the idea that Sansar can spin up as many separate instances as needed to support all those guests. I think one thing that would help make an event like that fly would be if the entertainer(s) on stage could be present in all instances.
Picture it this way. Someone who has "multi-presence" enabled is only seeing one instance at a time, but everyone in all instances sees them. Their voice output would also be heard in all instances. Ideally, the entertainers would be able to jump around among instances.