Your effort is truly appreciated, however I personally think that your method should still be classified as "Edited MTL". At the end of the day, even DeepL can't get all the sentences properly and if you don't know Japanese catching the error with game's context alone would be borderline impossible.
I was preparing dataset for Sugoi AI and stumbled upon this:
The original Japanese:
`“スクールカースト”という言葉を、知っているだろうか?
運動能力、学力、容姿、ファッションなどカリスマ的要素を持つ学生が上級階層者として実権を握り、そして下級階層者を虐げる。`
The pro translation done by MangaGamer:
` They say there's winners and losers in life. `
The translation DeepL gives:
` Have you ever heard of the term "school caste"?
Students who are charismatic in terms of athletic ability, academic ability, appearance, fashion, etc. hold the upper echelons of power and oppress the lower echelons. `
Translation is not rocket science, and sometimes there's a lot of ways you can go about this. There's no one-size-fits-all approach in translation.
The closest to the Original is the Original itself. But the point is for you to be able to play the game and understand most of it.
Even in movies like Matrix there's errors in translation (English to Russian), done by PROs. Glad I know the original language. Otherwise you lose some important clues about the movie.
I agree on one thing, you have to know the language to some degree to make better and more accurate translations. The thing with using MTL as a base is that it takes more time to do a fan translation, since you need to understand and check meanings for each word sometimes. But in ero-games where story is just optional most of the times, or just straight garbage (word garbage, no better than MTL), it' doesn't affect the gameplay.