all you need from naza is the signal wire like that diagram. The ground is all the same, the positive is all that's rerouted esentialy through the bec...... other end of the bec goes to the battery that's not in that diagram..... On mine i use 2 plastic servo ends on the servo and a female servo end on the bec so it all plugs together real nice. It was a castle so to program it was still able to link it up with castle link, change voltages, etc.
Is it possible to power the servos from the receiver (red and black) and take the signal wire from the Naza?