Flyable as in RC, I assume? The electronics gear will limit this, but it'll be hard to fashion something much smaller than what Horizon/Parkzone already has. After all they built their RC bricks to make UMX the planes.
Take away the RC requirement and that can get pretttttttty tiny very quick . . . but it becomes yet another eyesight challenge.
Have you noticed they're a very visual group? Eyesight challenges are cool, but don't particularly make good video.