Multi-Screen Streaming
For streams with multiple camera angles/screens showing at the same time, I think it would be beneficial to be able to stream them all as seperate "options" and have viewers individually decide which one to watch (with the ability to quickly switch between different options).
(Example: Players P1 and P2 are streaming their multilayer game together with seperate computers, but on the same stream. P1 is building a house, and P2 is exploring. A viewer decides to watch P1 build, but P2 finds something interesting. Since the players are connected together on the same stream, the viewer can switch to the view of P2's screen quickly and easily.)
I think this would help streamers that currently do split-screen streams, they wouldn't need to worry about manually changing which screen is currently featured, especially for situations where something suddenly comes up and distracts you like gaming videos.
It would be great for viewers to be able watch their preferred content (using the earlier example: viewers that like building can watch P1, and viewers that like exploring can watch P2).
(Statistics showing how many viewers are watching each screen might also be helpful for streamers).