Since the author is reading here, one feature request: Please put a volume slider on it and also make a mouse wheel scroll on any part of the page change the volume.
I think it's the lack of timeshift which triggers me so much, since it's a somewhat standard feature on TVs. No way to pause makes me a bit anxious. I have a bad habit of nesting YT videos, where I pause one, watch another, pause that one, watch another, when it finishes I go back to the previously paused one and so on until I end up watching the first video to the end.
Theoretically you could add a per-client timeshift feature.
I really like the no pausing / everyone being in sync aspect, it's maybe the best feature