the increase in resolution would still be very noticeable

I'd rather have "mind blowing" over "noticeable", getting as close to retina resolution as fast as we can. That will have huge implications for everything from VR media consumption (want to watch a movie on a 75" TV or a 70' movie screen while on an airplane, with the same fidelity as real life? No problem.) to desktop application development, VR teleconferencing, etc. It will also make VR games much better.

We can also increase FOV, but via some other means that wasting these precious pixels where they can't be resolved.

The non-foveal region of your eye -- almost all of it, everything outside of narrow purple spike here -- is already at retina resolution with the DK2. Increasing current FOV is putting more pixels in the far peripheral region of the eye, which can't resolve any detail you put there. Try turning your head viewing this web page with the corner of your eye. It's blurry patches of light, at best.

So rather that putting precious, precious pixels there, perhaps we could put a few very low res displays to create a sense of peripheral vision, amplify presence, without creating a huge rendering burden for pixels that can't even be resolved. This idea goes back to at least 2005, and Microsoft has built prototypes which are apparently very effective despite being insanely crude.