You want some formula tuned devices? I fiddled out most of them and made basic presets: [Effect Presets] tuned keytracked effects formulas/doofers Ktrk 1.1
I think I tried polynomial approximation when I wanted to make these devices, but in the end I found I had most going already with more simple, accurate curves. The filters follow a (scaled/offset) logarithmic curve, taktik had disclosed the formula and I got it going in my presets. The others are also mostly simple, i.e. hyperbolic, linear or exponential.
The polynomials, I tried math packages, but got nowhere…I should try again one day. You might have a little error in such function, but it should work. Sampling some data from the effect first, i.e. with a script reading back the frequency, then you can make an approximation for a formula device code. This could also be feasible for other (VST) effects, where you can read back the frequency of the effect somehow. Generate data, approximate, keytracker → tuned!