Thank you all for the suggestions! I have added support for /deop. It has the same password as /op, but different permissions. Make sure to update your config file, otherwise, messages may not work properly.
You can delete your config, or you can add the following line to your config.
You may also have to change some messages to use %command% otherwise it will say "JavaSE tried to use /op" when the command used was actually /deop. See the default config on the main page.