I'm most of the way through the Japanese track now, at least enough to give some more info on it. Technically the Blu-ray used the exact same dub as the LD, but they mysteriously swapped out occasional sections and put English voices back in, with subtitles. We'll get to why in a second. Nevertheless it was good that the dubs were largely the same because it would have been hell to try to sync the LD track if they weren't.
First, the LD dub isn't all Japanese either. For most singing parts, it's still in English too (Robin's minstrels, the entire Camelot scene, etc). So for that, we will still need to have "forced" subtitles on the Japanese track. I haven't checked the French and Portuguese dubs to see if forced subs are required for those yet. So that's a pretty small extra job I forgot about. If someone wants to check these other BD dubs to see if they contain subtitled English parts, that would save me some time.
It looks like they swapped in English whenever the LD Japanese dialogue dropped a line they thought was important (such as "We found a witch, may we burn her?") or when the LD dub had alternate music that maybe someone didn't like (reading the writing in the cave). Oddly, the new Japanese Anthrax scene has different background music, perhaps to cover up a few lines of narration they didn't like. I'm not sure what the narrator says in that scene, but it sounds incredibly over-the-top cheesy and I can't wait for the translation. And then there's scenes where I just can't explain at all why they reverted back to English (the whole of Scene 24), but nevertheless they did.
Anyway, the synced LD track sounds mostly great with a few glitches, some of which I can't entirely cover up--for example, there's a distinct glitch right when the Castle Anthrax cutover to the additional footage happens. I'll do my best, and the result will be lossless mono. Huge thanks to Silverwook on this--I definitely could not have done this without you--and I hope to hear back from my Japanese counterpart in the next couple weeks for the fun subtitle work.