1080p 30fps instead of just 1080p 60fps (Source) will be great for people with limited internet connection, you can experience quality of video similar to source but at HALF THE BANDWIDTH.

Right now there is option for 720p, 720p60, 1080p60 (Source)
Just add an option like 720p, 720p60, 1080p, 1080p60 (Source)

I have watched people who actually stream at 1080p30 it is a better experience than 720p60.