I love this type of thinking. One can then build a pack to meet all the specs. If it meets the specs but isn't satisfactory then relook at the specs to see what needs to change. Too often, in my opinion, packs are built to look good.
I would add 2 things to your list:
(1) Pack should be easily adjustable in as many ways as possible. My pack, for example allows for adjusting the back and front bags in relation to the frame and adjusting the frame in relation to the hip belt. This allows for changing things depending upon weight, terrain, up hill, down hill, tiredness, etc. Changing things often allows a tired or sore area of the body to recover and/or prevents it from getting more tired or more sore.
(2) Some method of balancing the pack forward to back is essential. One shouldn't have to strain forward, particulary when going up hills. Visualize a person carrying a canoe at the mid point, over their head, with equal lengths of the canoe ahead and behind. That's the type of balance I'm talking about. I used to achieve this with a high loaded pack frame that tipped the balance forward a bit. I now use a front bag. I once hiked with a guy who addressed this by bundling his stuff into a U shape and laying it horizontally on his shoulders with the legs of the U extending forward to shift the load forward.
I'd also like to add a few things about the waist belt, already mentioned by you. I'm for having all the pack's weight transferred to the waist belt but, as you say, there isn't universal agreement on this one. But I think most would agree that a good fitting waist belt is really important. A good fitting 3 ounce waist belt will add more comfort than a poor fitting 12 ounce waist belt. Making them slightly conical seems to help a lot. Material must also hold its shape. Some stuff stretches and after a few hours of use you'll find that the effective width of the belt might be down to about an inch running down the center. Not good.
I don't think I could make a pack that everyone would find confortable but I have been able to build one that I and some others find comfortable. This comfort thing is elusive and personal. Heck, some people in the world are comfortable carrying heavy weights on their head.
Where would I add some wieght for comfort? I'm satisfied with my current pack and so tried to answer the question in relation to it. I couldn't come up with anything to add for comfort. Adding weight to my pack could increase durability....but that's another discussion.