So your primary concern is using less bandwidth in what used to be called 'the last mile'. That still exist and is 100% dependent upon how a student connects to the internet ... not just Moodle.
So the use of RTMP ... here's one page that talks about a private rtmp server ...
on that page it states:
"If you don't have your own box, a VPS can also work. I recommend Linode or Digital Ocean as providers. Just make sure you have enough bandwidth...remember that bandwidth usage will be (the size of a stream) * (the number of people uploading + the number of people downloading). So when I have 2 streamers stream to my server, and I download both of them, I can chew up 10GB of bandwidth in 2 hours."
That talks about bandwidth usage from your server ... **not, however, the last mile**.
Could you ask some of your more tech savy students to test their connection to the internet for speeds/bandwith?
'spirit of sharing', Ken