I would like to be able to put the browser window where I want it on my screen space, put a pin or some other method to indicate how to act, then when I select fullscreen on the video I'm playing it fills the pinned window and behaves as if it was fullscreen. No border, no browser controls... Press F11 prompt from the content. Yet it is still confined to the space and size I defined.
A feature like this could result in having multiple sources streaming to multiple seemless browser windows. You might bake in a volume button to select which window has the talking stick. (something easy to toggle for each window) - perhaps the ability to have more than one window with audio output and different volume levels for when The Wizard of Oz comes on.
Just my ideas