Maybe I'm wrong, but I can't see why you couldn't do away with the boom altogether and just have a solid mounted winch and then a pulley at the rear edge of the deck for the cable to roll on? Any reason why not? I think that would look a little slicker....good ideas in here tho!
If I understand correctly, you would still need a ramp for the winch to pull the machine up. The boom lifts the sled up from beside the truck and it just swings over onto the deck. No ramp.