For this the mod would need to be fundamentally rewritten, so I would squash some bugs first. The idea I have: when a person places a PC case, that PC is assigned to that player and only that player can access it. When that player starts the PC, the VM runs on his system. Every second or .5 second, a deflated screenshot is sent to the server, which sends the screenshot to the other players.

Preview entities have to be rewritten, maybe they still spawn but only on the client world. The tablet / order system has to be just partly rewritten, basically the server has an ArrayList of all active orders, or maybe a Map<UUID, Order>, and when the player sends off the cart on his tablet a packet is sent to the server. The delivery chest spawning and movement should be managed by the server, or maybe the delivery chest spawns server-sided at the position where it should be but the landing animation is still rendered on the client-side.

For screens to work in this environment, you would need to add cables to connect the screens to the computers.

I will edit this if other things come to my mind.