I figured you'd already given that some thought :) I'm very curious to see what devs come out with for Quest on a grander play scale. I also like what I'm seeing from the Magic Leap AR headsets. Every-time I watch a demo I consider how I'd rearrange my living room for a tactical shooting game. It's definitely a different way of thinking... VR = clear your play-space as wide as possible. AR = move large furniture into you place-space to duck for cover.
Large enough play areas (I mean 25x25 meters) might be enough to allow for infinite movement. By rotating slowly world around you in the game, you should be able to go in circles in the real world, but in the game, you would be going in a straight line. At some point it could become a part of the headset API, so the game developers would not have to think about it and the player would have the same system in each game.