LAST UPDATE:
After A LOT of technical problems (that I spare you to know, it's so boring...), I finally finished to encode the movie using my ColourMatch2new script; it worked pretty well, as wrote previously; in the few frames with artifacts (still to check the whole movie, though) I managed to make some further corrections, but...
The problem is, x264 crashes after few hundred frames, maybe due to the high memory and CPU requests asked by the complicated AviSynth script, and the low power of my system... nevertheless, shots with artifacts should be few and shorts, so I thought to use this last tweak sparingly, and here you are the result on the most offending frame:

Not perfectly regraded as the DVD, but still better than the original BD, color wise, and so all the movie will be sourced from the BD, avoiding the use of HDTV or upscaled DVD shots; I also decided to use the old ColourMatch script for very few shots, like the "green bearded Neo", where the new script clearly can't beat the old one.
So, I'm near to the V2.0 - until I will receive the laserdisc rip of the movie; then, I should redo everything from scratch! (^^,)