Quote Originally Posted by ahyangyi View Post
I'm wondering where do the mechanics of the Sword Schools come from.

No, I don't mean the Book of Nine Swords. That's where the themes come from.

But Bo9S does not come with the move customization thing. Where you stack modifications to one of the many basic actions available.

Are these LawfulNice's original ideas? Are they influenced by Exalted? Are there game systems with similar promises?
Not Exalted no. Exalted's martial arts are pretty set in stone in their moves. You learn Single Point Shining into the Void Style (aka Iaijutsu for Solar Exalted), your pretty much mechanically the same as anyone else who learns it, the hope is as an Exalted your one of the few who has mastered it to that level.

the only game system I know of where you can customize your martial arts is Anima Beyond Fantasy, but lawfulnice makes no reference to it, probably for the best because ABF isn't exactly open to be used for jokey tones like this. but I don't doubt that there might be other systems that do allow for it.

at the same time it wouldn't surprise me if lawfulnice didn't know about any of them and came up with it on his own. most ttrpgs either aren't well known enough to have the jokes and memes built up around them or don't have much potential to be joked about.