My friend, you just keep making this exponentially better!
I do have an idea, though; programmable routers/bridge ends/overflow gates/etc. When you click on it (as when selecting an item to sort for a sorter), have a window pop up that has togglable '<]' & '>]' symbols (like you see when offloading materials from your vehicle) for each of the four directions. That way, for example, you can use a router beside a factory without worrying about output clogging an input flow or have an overflow gate only output extras through one side.
Does that make sense?