I read the script before commenting 😉
The bulk of it’s just Spline36Resize and AWarpSharp2… and I already use debanding filters on everything I encode, and ColorMatrix on everything I upscale, and a function to simplify the use of MDegrain2 is part of my arsenal (in fact I used it on an mp4 encode of the SSE of Star Wars, as well as on my DBZ encodes).
The current filter chain I seem to prefer for upscaling anime is a variant of nnedi3_rpow2(2).ColorMatrix(mode="Rec.601->Rec.709").Spline36Resize(1280,720).AWarpSharp2(depth=10)