Random suggestion: Reflecting on the Breaks, why not make them Zodiac subject? The fact that they're not is a strange thing about them right now - they're a "free lunch" in that you can use them to destroy someone who is largely ineffective against you. FFT doesn't have many PC-available offensive moves that ignore Zodiac (Dance, Item vs. undead, and certain Limits are pretty much it?) and Battle Skill probably doesn't deserve to be elevated to their company. This also puts a slight leash on its ability to boss slay (no greater than the one on Life Drain, granted). I dunno if Battle Skill's specific coding prevents this, but something along the lines of what Stigma Magic used to be (something near 100% at default, but still fluctuates with zodiac) seems reasonable. And this should work by making the K values of Battle Skill 80+ (depending on where you want the base to be) and using the old formula, from my reading of the BMG.
Re Mr. Cranbud's concerns about Speed Break, well, I guess my issue here is it's always been this good a move against Zodiacs. Yeah, it used to miss, but it also used to be Speed -2 instead of -1... the average performance was actually higher because its hit rate was over 50% (except in cases of bad zodiac, which I am all for changing). This didn't strike me as widely considered to be broken against zodiacs. Effective, sure, but not broken, and I think that's where it remains. It is -good-, mind, and people are more likely to see it in LFT than FFT because both Battle Skill and Knights themselves are more worth using in the first place (whereas in FFT, Speed Breaking bosses was almost the entirety of the skillset's use, along with perhaps Magic Breaking them). Though, to be fair, it's easier to get Two Swords, via Thief, which matters a notable amount for Queklain at least.