Teaching Winlink with an Audio only network

I have put together an "Audio band network" where audio cables from the sound card of a laptop are distributed to a classroom full of similar laptops.
The wires substitute for radios allowing many users to talk to each other. It works well for teaching FLDIGI and many other digital modes and protocols where each station is independent. Details are available for the asking.
I want to expand this to include Winlink. I plan to set up one computer running RMS Trimode in "radio only" mode. Of course there will be no radio to control just a sound card to make and listen to the appropriate noises. I want to configure the pretend RMS to store messages locally until the station with the given call sign checks in to get his messages.
I am seeking suggestions for how to configure the pretend RMS so that a simple call sign will be a sufficient address. Perhaps I need to designate the pretend RMS as a Home message server for those attending the class.

An Audio band network for teaching digital radio modes and protocols
Winlink Linkomatic