What alphabets do you need? In particular, do you need Kanji? If I understand Sephirok's previous explanations of the game engine, any character supported consumes texture memory and increases the amount of video memory needed to play the game. Therefore I think support of Japanese Kanji characters is not realistic. On the other hand, the Hiragana and Katakani alphabets are compact enough to be supported by the game.
What you could do to help yourself, is to replace the DejaVuSans.ttf font, that you can find in the game installation directory under data/video/fonts/Plain, with a JIS X 0201 encoded font, i.e. Japanese Katakana characters in the place of the normal Latin-1 accented characters. This would give you access to Katakana, and allow you to start on a translation. If the translation is making progress, maybe it can be considered to add the Katakana Unicode characters to the font engine of the game.
Please also take a look at this thread, how Russians did the same trick, before the game supported cyrillic characters.
http://steamcommunity.com/app/287580/di ... 442086731/
Unfortunately... despite some activity, there seems to be little progress with a Russian translation. Definitely do not underestimate how much work it is to translate these files.
So I started doing work on a Dutch translation am am progressing quickly. Now I would like to ask what the policy is regarding additional languages: Those files are copyright sensitive and I still remember when 15 years ago Infogrames sent their lawyers after fans who were working on translations of Civilization III 
