The new Zone system I just added today will work with World Composition (I just tested it). However, I don’t think you are going to want to do that for performance reasons. Even if you get the client to only stream the levels from the server that it needs (I was not able to get this working, but there is a new undocumented option for it in 4.14), by using world composition you will be forcing the server to run content you aren’t using. You will have to test the performance to see if it will be possible, but my guess is that it will be a waste of resources. The new Zone feature is in Test Version 8 which is up, so you can give it a try.