We found a UST para hatchet on the mountain a few years back. It had been laying there at least a year and was in good shape and still sharp. Get one with a secure way to carry it, if not in your pack. A heavy head helps with splitting the ribs and pelvis. Too short of a handle and you can't get in the body cavity to split the bones. Neither of us carries one while hunting but have a gerber in the truck or camp if needed.
The word hatchet and lightweight just don't go together. To be useful a hatchet has to have some weight behind it to keep you from working your rear off. If you are in a area where you are going to be packing meat out look at doing it boneless, so no hatchet is needed. For around camp I would just use a Wyoming saw. Either their small or large one. Neither one weighs that much and they come with a bone and wood blade. I prefer the larger or the Wyoming Saw II if I am going to be cutting bone. But both work quite well.
Hatchet on a backpack hunt? To much weight, LOL. Bring a Wyoming saw along, much more useful with a meat and general blade. And besides, a hatchet is dangerous and I try to limit my potential to do something stupid with a sharp object.