I still like Zep's Pic #2 design as the best option so far. (Of course, it may look good to me because it is crossing a mountain stream!)
That design requires much fewer materials. I like having the hand rail.
I also likes RAH's addition of the sand paint to walking surface.
I have never planed a long timber with my chainsaw. Does anyone know if an average "craftsman" would cut a suitably flat and level walking surface?