Amano's art isn't exactly on your side.
Since you're done, I'll just summarize your whole argument.
"Final Fantasy 3's "Makenshi" are Dark Knights"
- They were later re-adapted into Dark Knights in the DS release
- Them using white magic doesn't matter
"Cecil did not use Katanas"
- Amano's art has a cross guard
- Dissidia's classic DLC shows a "stylized sabre"
""Mahou" and "Ma" are not linked at all"
- Because anime is meaningless
Problem areas in your argument:
- "white magic doesn't matter"
- attributing too many things to "ma", such as dark, and curse (dark =/= evil; evil =/= dark)
- ignoring Final Fantasy: Unlimited because it's anime
- ignoring that "mahou" has been classicly demonic, and has only become "good" due to anime
魔法 - Mahou - Magic
魔剣士 - Makenshi - Cursed Swordsman/Magic Swordsman (FF3's job)
暗黒騎士 - Ankoku Kishi - Darkness Knight (Dark Knight)
If you just examine one words meaning, then you arrive at the conclusion that Makenshi is a Cursed Swordsman. If you factor in that SE has been continually taking away anything demonic related to Makenshi, then you can determine that Makenshi used "ma" in the same way that "mahou" used "ma". In short, you could say this is the anime definition of Makenshi, rather than a literal one.
As they came up with Dark Knight, they pulled abilities and traits from things they had made in the past, resulting in Dark Knight using some of the more dark-related aspects of Magic Swordsman. To remain consistent, when they revisited FF3 for its remake, they replaced Magic Swordsman entirely with Dark Knight, as they still needed something to fill the role that Magic Swordsman filled then.
In the anime you want to ignore, Final Fantasy: Unlimited, there is a character literally named Makenshi, who's name is meant to describe the actual character. He wields a sword, and uses magic. Nothing about his seems dark or evil, in fact, his nick name is "white cloud", as he summons a Mist Dragon, while his direct counterpart is Kaze, nicknamed Black Wind. But this is all irrelevant, because although all of this is literally Final Fantasy, it is also anime, so it doesn't count.