Mount the drive with the user or group as plex. See mount options uid and gid. You can also set precise permissions on the mount point (using options at mount time) to let plex access a subdirectory.
I think the command pattern would be useful. The user requests to perform a command. The command implementation can define preconditions and actions that mutate your game state.
You could start with a multiplayer server that handles the game logic, and a command line client that that can interact with it, create a game room and invite someone to it. You can handle realtime communication with socket.io. Once you have the client and some game rules, you can implement the client on a frontend using a canvas or game engine. You could then add the bot opponents using simple random number generation and some basic strategies.
@ClemaX
@lemm.ee