Keeping image/video/audio data out of process actually sounds kinda reasonable to me :-).
I think the really compelling example is cross-origin script loading. I can't imagine a realistic way to keep the script data out of process but let it be used with low overhead.
Oh, I think it's doable; the question is how much the memory overhead for the extra processes is.
I agree that doing this for script (and style) data is much harder from a conceptual point of view! On the other hand, the protections there are already much weaker: once you are running the script, you can find out all sorts of things about it based on its access patterns to various globals and built-in objects (which you control).
I think the really compelling example is cross-origin script loading. I can't imagine a realistic way to keep the script data out of process but let it be used with low overhead.