I like the idea of taking old laser tag arenas, kitting them out with lighthouses, and then having vives hooked up to backpack pcs. Battery life is only an hour or so, but I'd like to see you last an hour of running around a jungle/glacier/moon/starship/wartorn village. You map the physical space into a variety of play arenas built in your engine of choice, so that snowdrift corresponds with that pile of foam, this bridge is that ice bridge, that room is this room, etc.

The tech is already here - the hurdles are pretty minimal, it's just a question of setup.