Rope ladders are singularly useless, even for kids and tree houses, however us pirates could maybe benefit from the concept: Some people need to use the strength of their legs to climb aboard. Something that allows them to get a foot or knee purchase. How about a "single rung" rope ladder secured so the rung lies along the side of the hull, say at about waterline, when deployed? That way the rung can't get away from you when you attempt to climb. A 2 x 2 wood running board for boats.