Exactly! The swap requirement is the concept behind my arrangement as well. I don't normally carry the watering can with me outside, there the fishing rod takes its place. In the mines, I always keep a chest at the entrance where I drop all the tools in except for the pickaxe and the sword, then the bombs go in the first three places. The food has to be just to the right of the sword so that I can switch quickly in case of deadly danger.
I play on PC, but I don't use the numeric keypad, but WASD lefthand and mouse righthand. I always use the mouse wheel to swap. Runs like a charm.
It's really interesting to learn how differently people are wired!