My brother and I dropped two full sized cows in the bottom of a very bad hole in NE OR early one morning, when I was in my 20's. We had a party of 5. Only 4 agreed to pack a quarter out the first afternoon, 4 mi one way, with most up hill, 8 mi total. The next morning only two of us answered the bell, my brother and I each took two quarters in one trip that day. Mid-Nov, so meat care was more about how long we had to let it thaw to process at home than worries about spoilage. My point is yes you can do it, but make sure you know the capabilities of the entire team, it is as much mental as physical. Knowing what I know, and being older, I'd either have a packer on call or check into Llamas. I don't care to care for horses, and have zero experience with Llamas, but have heard from others they are very easy to care for in the back country. If you know for sure all of your team has the attitude, equipment and capability to do the packs you describe, no reason not to give it a go.