I know Kodi has Pseudo TV add on that can add YouTube subscriptions and I wish Live Channels was as flexible as Pseudo TV or did something similar.
maybe with some super wizardry of CumulusTV (it can set websites up as channels)
youtube has URL parameters to have a link showing the video in fullscreen/autoplay/quality.
There was a way with PuppetMaster. If you could find the streaming url for a YouTube live tv channel (not the regular YouTube address, an actual streaming url that YouTube keeps heavily buried) you could add it to PuppetMaster via its 'Scrapey' plugin.
Channels from Scrapey can be set to appear in Live Channels and this worked fine for a while...
The problem, apart from finding the url, was that the streaming url would change every so often (behind the scenes) and the channel would stop working. The actual YouTube public url adapts to the changes of the streaming url and the viewer is none the wiser, but anything that's relying on the streaming url will stop working at some point.
I haven't used PuppetMaster in a while so I'm not sure if things have changed.
Also interested in this!
Google should make it easy for YouTubers in to integrate the channels. They should be able to easily curate their own channels with playlists of there old content. And then break to live whenever they start a live broadcast.
Just like cable.