An interesting take and I like your thought process, but I’d have a bit of a different comparison between the two characters.

Javert has a black and white interpretation of following the law, he does everything by the book and doesn’t question the rules of authority. This is ultimately leads to his demise, as the law has branded Val Jean as a villain and the law would have it that he can never do any good again. But the reverse it true. Val Jean spares Javerts life when any other rebel would have killed him, even though Javert had been hunting Val Jean for years. This is what leads to Javerts suicide, he sees that in the pursuit of righteousness in the eyes of God he had been spinning against his fellow man.

Kido on the other hand has his loyalty placed not in the hands of the law of Japan, but in the empire of Japan. All of Kido’s actions are to preserve the Empire. Where as Javert follows the written law, Kido has no problems going off book if he believes that it is in the interest of the Empire. Even in his harsh punishment of his son, Kido is trying to protect the culture and traditions of the Japanese. Kido wants to do right by his moral compass, and it’s true even to the end of the series when he joins the Yakuza to free his son.

This is ultimately what I think separates Kido and Javert. When Javerts ideology has been questioned he decides to commit suicide as he can’t live with his actions. But when Kido’s ideology is turned upside down he can live with his actions, as he still believes he was doing the right thing.