I just don't think battery technology is refined enough to have a dependable train layout unless you want to spend a lot of time on battery maintenance and charging. Batteries for RC airplanes are finicky, short-lived, and relatively expensive. I usually settle for Ni-Cd or Ni-MH batteries and accept the higher weight just to get some longevity. Many don't even want the Protosound 2 battery; they replace it with a BCR.
Also, three rail track with the center rail removed is still gigantic (try it), which may explain why S gauge (usually) offers both hi-rail and scale track and wheelsets.