Would it be possible to use plugin messages without a player online on the sending server? Like creating a fake player with localhost connection? Yes I know there are sockets but that would require a new system for my servers and the plugin message thingy is easier to use and already setup. Would that work? Because I want to send a message to all staff members when a server shuts down and starts and atleast on the startup there is no one online.
Unless this fake player is created either on bungee, or through an executing script outside of the server (like a bot) then no. Creating a fake player on the specified server wouldn't work as it has no touch with the bungee side. You could however create a bot, that is just always online, and then it uses that bot as your plugin message sender. But then now you are designing a bot, which if getting the messages across are really something that important, you should probably be using sockets instead.