A few years ago a friend of mine was building docks. He needed a small log loader to do demo work and pick up poles. He made his out of 3x3 tubing and the swing post was a set of thick wall pipes that slid to gether he used tapered roller bearing out of an old scraper rear end but smaller 18 wheeler wheel bearing would work on one. He even built the power rotation grapple. It would pick up 2500 pounds at 22.5 feet. One smaller could use some smaller components. Hes sold that barge but I may can find a few pics of it.
Some great suggestions. The Nova trailer is great but it is only a 1:2 scale model. The Valby loader is perfect, but I'm scared to price it. Fabbing an old backhoe would be fun, but they are generally too heavy for my purpose. I like sizzami's design best. Good excuse for a road trip with a camera. If I can figure out how to send a pm, I will do it, but just in case, where in VT are you sizzami? I'm near Rutland.