The idea of having a supplementary pouch on your front is an interesting concept and one which a couple of manufacturers offer in the way of an option. I think Duluth Pack has one. But it reminds me of my very first backpack.
When I was in the Boy Scouts something like 55 years ago, I acquired and used a surplus US Army ammunition bag. It had two pouches, both without flaps. I believe it was intended for carrying two (or more) ammo boxes. You carried one in front and the other in the back. In theory the weight distribution is good but you don't want anything heavy on your chest like 25 pounds of machine gun ammunition. But Dick Proenneke used one, though not for backpacking. He used his for his camera equipment, mainly, until he began using an aluminum pack frame. He also used a surplus wooden army pack frame, too. That's what he used for "backpacking."
Thanks for your input.
Wooden pack frame? Not my idea of joy, but no doubt ok if it's made to fit the wearer.