Well, the only advantage I see in this is that you wouldn't have to minimize to search for another song, since it's possible to play YouTube in your browser while the game is maximized. It doesn't hurt since it's up to each person to decide what to listen to and when, but I don't think it's worth spending scripting/debugging time. Maybe a suggestion to "share" your music with players around you would be better. For example, search for a YouTube song and play it for the players inside the vehicle you're driving (hell, that could be motivating for teamups!) or maybe even players near it. Something like a car radio? I would make it a VIP feature though, just to prevent trolls from streaming annoying or offensive sounds. Also there should also be a new parameter in the recently updated /ignore command to ignore music from a certain person or from everybody but yourself.
I personally wouldn't be interested in using this, but I believe it could become popular.