Well, this is probably the wrong place for Star Wars ;) but the HSL recombination can be useful in assorted instances. I found out in PDB's Blade Runner Color Regrade that anomalies become magnified, as you've discovered. My last conclusion there (without having best sources for further HSL recombination tests) was in favor of a RGB color correction (Page 3 that thread).

I had better success in first equalizing the Luminance of the separations before recombination in muddyknees2000's The Hobbit Rankin/Bass Animated Film (see Page 4 that thread). In that case, the VHS look (at better resolution) was the target. The DVD was too dark to accurately carry the VHS Hue & Saturation. A "color correction" of the B&W DVD Luminance was first made to match the VHS Luminance (very easy with B&W only) before recombination.