For information: I just sent a message to Dingwall tech department. As you said, it seems that I should buy and install a "3X Rotary Pickup Selector" in order to have an NG2-like configuration (as the attached image shows). It costs 68 Canadian dollars and I imagine I will need to ask my luthier to help me wiring it, as I'm not very practical with these things. I'm still a bit confused. I don't understand at all their choice of putting a stock D-Bird selector in NG-3 models, cutting out the signature sound this bass has been designed for (as Nolly wrote, the Bridge+Middle series is his favorite configuration). I guess you can choose to have the Rotary Selector already installed when ordering your bass directly from Dingwall, but it's also true that NG-3s sold by online shops usually come with a D-Bird selector. Again, a really strange choice.