I thought about this option, but I would still need to either relocate the dump nozzle, or cut out a hole for it in the bed and then be okay with a very tall lift (these flatbeds sit high already). I could be wrong, but I think the jack extenders would need to be custom built. Personally, I am not super confident that the rear jack mounts (specifically the backing wood) could safely carry the moment that would be created by offsetting the jacks. This is definitely a viable option though.
What got me thinking was that I parked next to a flatbed and decided to stick my head under there and see what the layout of the structural members was. It was surprisingly simple and sparse. Assuming the beams are mild steel, the mod would be fairly straightforward for a fab shop or fab hobbyist. The only downside is that the flatbed is not going to be useful for much else after the mod.