That's kindof what I was thinking.
a two-stage throttle was one such. Nothing complicated. Just a light return spring on the first part of travel, then a heavier one on the latter part, with an adjustable sliding stop to change the cut-in point.The springs were chosen to make the cut-in point obvious.
I used coat-hanger wire bent into an elongated S shape with one long leg, and a wire clamp from the lawnmower dealer;real simple. Drilled a hole in the throttle return-spring anchor for the long-leg.Took about 10 minutes to build and set.
I'm still not a racer tho.