create .6 manual package-addressing station
Connect it to your postbox, perhaps, if you do want to handle package transport with trains.
right click depot with an item named for an address
smart observer detects (anything) in the depot, sends a signal out
sticky piston pushes an observer into the block under the display link, updating the sign on the packager with the name of the item in the depot
second observer + droppers is a system to set the display link to Always On so it doesn't do its "occasionally update on its own" thing
I'll be honest, I don't know what's causing the droppers that get hit by the second observer to swap their items in one of the states -- it's doing what I want it to do, to be sure, but it was a happy accident. my best guess is some quasi-connectivity nonsense
packager can only output when nothing is in the depot! this should be fine.