As an alternative to the big steam and diesel trains, I'd love to see an electric commuter system like the People Mover at Disney. Those things were zippy and relaxing to ride.
A shot of the doors closed
http://www.laughingplace.com/guide-attraction-26.asp
A shot showing the doors after sliding open (3rd pic down)
http://www.onlywdworld.com/201…-attraction-vehicles.html