Here's a cool bus. I photographed this at Middle Tennessee State University in Murfreesboro, TN.
They used cattle railing for the deck railing -- the stuff that stockyards use for temporary corrals. It plugs into sockets at deck level.
Back porch is made by cutting frame about 1 foot or so from rear bumper. Bumper and stub frame pieces are then extended back from the bus by some 6" angle iron that is spliced in by bolting. I think a really clever person could make a retractable deck with this idea.
More pics here