I know that the plugin can only block the command like give but is there a way to modify this script line to block it from spawning some items shortnames "if (!config.BlockedCommands.Contains(arg.cmd.Name) && !config.BlockedCommands.Contains(arg.cmd.FullName)) return null;" ?

There are plugins for that, so I don't think that is necessary. You can also use the Give plugin if you want to restrict the item giving commands.