Really fun idea! I'm quite not convined about the control scheme though. I feel like the Pick Up and Drop actions should be doable with the mouse (Left Click to Pick Up, Right Click to Drop). A game like this may benefit more from allowing the player to just focus on movement with their Left Hand on WASD and make all the other actions mouse-centric. This way you don't need to worry about having to keep track of buttons everywhere and can focus more on trying to perfect the flow of actions and delivery by getting better at performign actions with the mouse. I also naturally found myself tryign to just walk away from the truck with WASD but kept having to remember that I have to click X to get out of the truck-view.
Just some quick thoughts!
Super fun idea though, I can see this being really chaotic and funif you further expand upon it with more stations (maybe special stations for special package-types?).
Nice work!