I'm not saying it wouldn't work in theory, I am saying it would not make a *human* driver faster. As soon as it overshoots one time unexpectedly, the driver will not be 100%. And it will overshoot every now and then such as when the driver decides he wants to back off quickly but was previously headed for full throttle. The ECU, with your approach, will say "here's that 100% you asked for a moment ago!" even though the driver now wants less. Remember, the throttle blade has physical inertia, the electric motor has limited torque, and there are digital filters and delays throughout the system.
That's why I say a comfortable driver is faster. When I set up ABS, a driver could beat it one of ten times for max braking force, but the ABS was fastest overall when it did the same thing ten out of ten times, even if the max force was slightly lower.
There are aftermarket piggyback systems that do what you are looking for though, so you could always try attaching one and trying for yourself. I wouldn't, but you can.
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