I can't see how that would work in practice.

What if you just don't sit down your bag on the weighted area? When I buy more bulky items, like cat litter or toilet paper, I usually put them on the floor. Also my backpack already has stuff in, which i sometimes take out and re-arrange while putting stuff in. Also what if you buy multiple items but only scan one and then use the number input to adjust the quantity?

Glad that we don't have that shit. Just a scanner and a wooden shelf for your bag.