not really impossible, but theres this rail around here down the middle of a set of stairs, i believe about 6-8ft down -> 1ft flat, about a 5ft gap, 6-8ft down, 1 ft flat.
the part that looks tough to me is that it moves on both axes, its a flat down flat down or whatever and it moves left to right, and not smooth, its angled. so if you actually made a rail for skiing that curved up and down as well as left and right, now that would be sick.