After writing my last post, I realized that an even better way to do this is to actually formalize the binding as a custom binding:

public class OneWayBinding : CustomBinding
{
   public OneWayBinding(Binding baseBinding) 
      : base(baseBinding)
   {
   }

   public override BindingElementCollection CreateBindingElements()
   {
      BindingElementCollection bec = base.CreateBindingElements();
      bec.Insert(0, new OneWayBindingElement());
      return bec;
   }
}

Then you can simply say:

CustomBinding binding = new OneWayBinding(new NetTcpBinding());

Windows Communication Foundation