first thing comes into my mind when its mentioned about speed is accelerator.

speed limit cut means to cut off the speed limit which was imposed on the vehicle. removing it means you can go faster. What you're trying to say your car has a turbo and force induction forces 1.2 bars of air pressure into your engine. I think both are different subjects.

Paddle shift comes only with the transmission and car design. it will require alot of wiring involve and normally most of the time new auto cars will have these feature. As for manual dual clutch transmission normally good sports car comes with the shifting option.

IMO its not practical to change to paddleshift system. I'm not sure if its possible but right now i have yet heard any one did it.

your button to pick up speed is quite ambigious. OD off Button is another way to downshift in auto pick up speed.