Cap'n your not far off... All this could be fabricated in SS pipe and polished or brushed very easily. Schedule 10 pipe would be very strong and a good fab shop would have a hydraulic bender to make the corner radius and contour. As discussed, the biggest problem is the issue of backing plates. But where there is a will there is a way. My current boat has some of those access plates so that they could get to the bottom of the swim platform to add the davits...
Now you would have access to the bottom side to add the biggest backer plates you could get through the openings.
I think the original poster would be better off adding an extended swimplatform with an additional handrail on the boat. The problem we are having is having to step over the angled sides when loading dockside. A straight out step would help to keep people more stable as the step aboard.