This is an awesome idea!! If of you hook this up to an a cobblestone generator or quarry, you could rapidly mine inventories of cobblestone and other resources and have like one cart for cobblestone, coal, one for iron, and one for diamond for easy sorting. You could even example this idea to make like a railway station with signs labling "deposit iron here or something and place the carts on unpowered redstone track with buttons to active rapid storage. While simple, this is a fantastic idea. Great job!
