Delivery boy is actually a good idea idea for a job. Arguably Cargo Techs might do this, but in practice, they don't.
On the first server I ever played, "mailman" was a selectable job one day of the week (it wasn't that day). I could see the old janitor's office being turned into a mailroom. A service desk a la the one at the kitchen, a disposal with a looping conveyor belt so received packages continually go in a circle like at a baggage claim. Add some package wrap, gift wrap, tape, crates, destination tagger, one MULEbot if we want to be ambitious. Perhaps a Rapid Crate Sender and a cargo telepad: now cargo can beam crates directly from the shuttle to the mailroom and just tell the mailman what to do with it. Mailman can beam empty crates back to cargo with the RCS. Give the mailman both supply and service comms, a message console and a newsfeed. Ambitious mailmen could set up a store at that location. Antags could really do well with that job, too. May need more room to make all this happen, and the more I think about it, I'd think that two slots could work.
You might say, cargo right now has the EXACT SAME layout I just described, down to the service desk. But I think that separating the mailroom from cargo could really make things interesting. Maybe cargo techs can work there instead of a new mailman job. Mailman or cargo tech, they should report to the QM.
A server I was playing on a few months ago had the mail room separate and a little room attached to the kitchen for the food delivery boy/girls and it was actually pretty interesting. There was a good balance of antag options being available with those jobs. Captain order a special meal just for him with the highest quality ingredients and you are tasked to deliver it? How about poisoning the food or slipping in a bomb into the box.
It may also help in moving that usual chaos and bloodbath that happens in front of the kitchen/medical if food is getting delivered to departments. Maybe give the food delivery person a little robot they can ride around like the janitor has (Your food to you department in 15 minutes or less).