I like the idea of duels but there should be an option menu that lets you choose say. No mcmmo or no /d or no /speed etc. I don't think even with mcmmo on it should give players experience toward their mcmmo because then they could just farm it. It would be a bit of work for the devs but would be completely worth it. :D
Wonderful suggestion and I would use it probably hourly when I'm on,
~Preston <3