Well, if you think it's cool, fine. Personally, I'd rather they used their resources for something other than this kind of complexity.
To be honest, I'd rather they used their resources for things like this rather than something other. It's just it'd be a quite unique piece of engineering - and I'm all for that. Game developers tend to serve us the same reheated dish time and time again, not really striving to push for innovation, changing only setting, story and resources. I'd rather have something new than just another iteration of the same.
Well, I admit that, being a developer myself, there's probably also a wee bit of professional curiosity involved
Maybe you could actually define your PC's nationality when you're creating a character? This way you could play as said Japanese and have all untranslated Japanese dialogs in the game, and for everything else have subtitles of various levels of accuracy. Wouldn't change anything mechanics-wise, thus eliminating large part of the discussed complexity, and there wouldn't be any real need for actual different language versions. Well, the UI could be set to whatever language player chooses for his PC, but that would be cohesive with the overall design. Obviously that would also mean that there wouldn't be any dubbed voice acting, but I still cannot imagine that anyone would want to have most people in an American city (however fictional) speaking their own language. Either we care about immersion, or we don't.