The big issue is the load has to be carried somewhere and a 15 pound child hanging from your lower back would be murder not to mention it would be in the way when you walk (worse than a sporran with 2 arms and legs). Add to that a person with a protruding belly and you will have quite a bit of weight leveraging on your lower back! Ouch, it makes me cringe just thinking about it. The only other place to anchor it is the shoulders.

Perhaps I've not noodled it through far enough to understand it but good luck putting it together.