I’m pretty loyal to Eberlestock and know you can use the J series packs as meat haulers even thought they are internal frame. Just take them to the car wash and spray them out good when your done. I have an X2 that’s day pack size but I’m in the process of modifying it to be a multi day pack in the 4900 cu in range by adding a spike duffle and some other attachments. Mostly because I’m too cheap to buy a new J-series pack.
I also have a Kelty Cache Hauler which I would highly recommend as an external frame set up. Last year I took half (boned out) of a friends elk 3 miles back to the truck with it. I’ve also used it on my own elk, taking camp plus a quarter in one trip then going back for the rest. It can handle more than I can carry I would guess.
Best advice is to get the best that your willing to pay for, my first year of elk hunting was with a sub standard pack. Lesson learned the hard way when straps and molded plastic frame broke under a heavy load.