Another issue (that was also already listed before in other threads) with the original idea: duellers get their money from duelling - money is "distributed" throughout all classes of players this way, following a standard food chain. If you want duellers to only duel duellers, where would the money for duellers come from in the first instance? What you are really saying then, is let's remove the duelling class?
The more I think about it (and I guess it is time to stop thinking about this thread now), the more I realize there is no way any part of this idea, or any variant of this will work.