So for some updates to this very old post:
I tried a few different 'hardware' solutions.
Chinese Pedal Commander: $26CAD
Results? Only changed how fast the throttle goes to 100%. It didn't change the throttle hang when letting off the pedal, and it didn't improve the input filtering. You can still hit the pedal 40 times quickly, but the throttle wont respond unless you hold an input.
Decided to try the bad idea as well. I knew it wasn't going to work, but had to try. Had the spare parts to test the theory.
What was most interesting is the firewall, carpet, and pedal all had pre-made notches or holes specifically to fit a throttle cable. They all line up perfectly.
The motor would rev up if I matched the pedal position to the throttle plate position, but otherwise would choke and throw limp mode at me. Worth the shot, but man I fucking hate the throttle feel in this car. I am creating a drift kit, but I don't want to force people to buy aftermarket ECU's just to open the idea of throttle control during drifts. Like, you can't 'pedal' these cars. You could if the throttle pedal and throttle plate were actually working together.