I'd like to get a dashboard view using the webcam feed as a background, with translucent widgets overlayed on top with HTML/CSS. Is this something better implemented as a standalone plugin, or perhaps added to OctoPrint-Dashboard? I'd also need to get OctoPrint-Dashboard supporting WebRTC, and then either maintain my own fork of that or get it merged upstream.
Thoughts on what the appropriate direction would be?
Something so specific would probably be best served creating your own plugin. To me it sounds like you're trying to recreate what others have done in OBS though for live streaming, so wonder if that's what you're attempting this for?
Well, the audience is me, and it may be that OBS is the best way to do it. Really I just want to monitor my prints using both a video feed and some widgets, and I think full-screen video with widgets on top is the best way of doing that. If putting that together with OBS is easier than HTML widgets over a <video> tag then I can consider that too
You may find what you want in a side project/application.