Actually here is an example with slightly optimised scripts (no re-computing of x,y when not needed)
P.S.: Frankly, though, I dont think you thought out very well your plan....IMHO this is not a practical way to control 4 faders - it will surprise me if undesired changes of values to one fader while trying to move the next or previous to it dont occur. I just tried my own creation, and franly Im lost as to how to control the faders without giving too much thought.
Also there is no way to simlultaneously control for example, fader 1 and fader 3 - or fader 2 and fader 4 and this of course is by design (by your idea). For intuitive control of 4 parameters (4 faders) I would just use a multiball with 2 balls where one ball's x,y would control the 2 faders and the other ball's x,y would control the other 2 faders.