Some thoughts from and bitter experience.
1) only squeeze the trigger once you are confident of the extraction, and if extraction will be a ballache then don’t squeeze the trigger
2) Roe sacks are mostly very poorly designed as a load carrying device
3) dragging is hard work. I am not convinced sleds make it any easier. If I drag then rope around head and just drag - if its grass, bog and its a little wet makes it a lot easier
4) well designed frame packs - aka American type packs are designed to carry heavy loads, and put the weight properly on your hips via the waist belt. And are long enough for most adult sized men. With a big load you want the weight properly distributed. Roe or Sika sacks don’t do this.
5) if you can reduce the size of the bits you need to carry. Consider that skin, bones etc will only be discarded at the other end so keep the haunches hole, take off the backstraps and fillets, and bone out the shoulders, and take off the meat on the rib cage. Plenty of crows, raptors and small birds (blue tits etc) all will welcome the pickings off the rest of the carcass. Worth chopping / breaking into smaller bits so that it can easily be dispersed.
But appreciate that in many places not really an option to cut up the carcass.
6) often though carrying considerably easier than dragging. Spreading the load with a few people really helps. A pole with animal slung below is traditional way of carrying a whole animal in many parts of the world. Stretchers and stretcher carts have been used / still are used in many places.
7) Quads argos etc all work but are expensive and can make quite a mess to the ground so not always popular. Helicopters are brilliant.
But if you can, best to take a beast where it is easily extracted.