Mini knows his stuff and I tend to agree with him on a lot. I don't doubt a better overall setup, like getting a BBK helps, but I personally choose to go about things by fixing things one at a time.
On the PP setup, the caliper does a fine job locking up the wheels with my 200TW tires from 130mph, but the modulation once you lock the wheel is where the sliding piston calipers lack. I almost always lock the front left wheel down the straight at my home track before a 55 mph turn in. I have fluids, pads, lines swapped. I just can't get enough cooling to the rotor, even with the rs3 ducts. A BBK won't solve that for me, but running some hoses to the area should. This winter I plan to put some NACA ducts under the front bumper behind the fog lights, with a block off plate for road use, and run the hoses around and mount to the arms, then just drill a hole into the stock backing plate. We'll see how that works. The other limiting factor is the stock rotors. They just don't move or vent well enough. I plan to go to a girodisc or racingbrake rotor and see how much that helps. I would argue most of the benefit of a BBK is from the two piece rotors and better lines, and the caliper is more a thing of "feel" and pedal modulation.