Not sure if the “new two finger side swipe gesture” is a viable option.
AFAIK, gesture support is from libinput, which leaves things out of GNOME’s hands.
I wonder if swipes can be accounted for by exponential acceleration, e.g. baseline gesture speed is e.g. 0.2 (configurable by a slider as you proposed) and increases the longer/further the event goes.
If my logic is correct, that would reach the original speed shortly, and the swipe would trigger as usual without any modification to anything other than clutter.
Best regards,