As title, it would be more convenient to compare multiple players side by side or 4 at the same time to help comparing skills between players like what osu official tournament using to stream. I don't know if this is entirely possible.
That would be a good idea! but what if too many crashes osu?Then you would need to decrease your number of concurrent players that you want to watch. I think osu would be able to handle this. Also since most computer for gaming nowaday have high enough specs, I don't think there should be any problem. For low end PC, there should be a limit on how many you can watch concurrently.