Well, it doesn't work like that.
The way transmissions work with the constant mesh gear pairs is the need to be unloaded to shift at all. Normally you use the clutch to disconnect the motor from the transmission and it gets unloaded. When the motor is under power, it is driving the rear wheel and the transmission is loaded and under tension. Interrupt the ignition and/or fuel momentarily and the engine stops driving the rear wheel momentarily and the transmission unloads. Shifts can happen now! But only quickly before the rear wheel starts to slow the bike.
Under normal deceleration, the throttle is closed, the rear wheel is driving the motor, and the transmission is under load/tension because of engine braking that occurs. You can't turn off the fuel any more since the throttle is closed and you can't kill the ignition either since it won't change anything. The transmission is still loaded in this scenario. You have to reverse the tension on the gear pairs to unload them. You have to pull in the clutch or open the throttle to make the engine try to drive the rear wheel again. The transmission is unloaded during this transitional period.
See the problem? There's nothing to kill or interrupt that would reverse the transmission in the case of a closed throttle to allow the downshift to happen. Quickshifter won't work for downshifting - AT ALL!!!
For the 3rd Gen ZX-10R (and 1st, 2nd, and 4th Gen also), the throttle cables directly control the primary butterfly valves in the throttlebody from the throttle housing on the bar. On the 5th Gen ZX-10R and a lot of the other later model sportbikes, the throttle cables tell the ECU how much you want to open the throttle and the computer then drives a stepper motor to open the primary butterflies accordingly. So it's a simple software update to tell the computer to control the throttle for downshift....
if (gear_select_switch_activated == true)
if (current_gear_selection < last_gear_selection)
open_throttle = true;
else if (gear selection > last_gear_selection)
stop_ignition = true;
throttle_value = throttle_grip_value;
Getting autoblip to work on the older bikes requires an expensive, complicated system that adds a control motor and a second set of throttle cables into the throttlebody to override and control the throttle opening to do it right. It's completely different than a quickshifter which just interrupts the normal engine operation that is happening to accelerate the bike. But in reality, any of these bikes come stock with the ability to clutchless downshift already. Just as long as you're willing to drop the motor, split the crankcase in half and replace the transmission parts that will be destroyed from doing such a thing every few months that is.
Just grab a copy and read Scout's upcoming book titled "Turns on the loop". Clutchless downshifting is the chapter between "Oil changes are a waste" and "Figure 8s on the slab".