Before you start on that, stop on over to sherwin william and pick up some emulsifier, to stop the rust. it's a 16 oz plastic bottle, and is bluish green in color.
put some in a spray bottle. it will kill the rust.
Prime it and paint it with rustoleum paints.
2 X 10's PT with a 1/2 PT plywood over the top
stainless steel, Eye loops for the tie down points