There might be a little electronic voodoo that makes it all work. All I know is that the system does a pretty good job, even if it is complicated. A mechanical LSD would not be a bad idea.
If you read between the lines in the interview, you get the impression things work pretty good with the Fiesta ST. With that being the case, be advised that any changes you make may throw off the balance that has been created with the suspension, brakes, and power. I am going to try a set of different 17" wheels and wider tires next month to see how that changes the car. I don't plan on keeping the stock wheels, but adding heavier wheels, a different offset, and different size tires may be the wrong direction. Heavier is surely wrong, but not sure how much difference it will make. With my 2011 Fiesta, adding the 17" wheels makes the car feel like it is a tug boat. Going with 14" wheels in the winter really makes the car feel quick. With 197hp compared to 120hp, the wheels might not be a huge drag. There are just so many things on the ST that just work. The more I drive it, the less I want to change it.