The font aspect I know is possible (in theory), though I'd have to track down my research on the font templates.

At the time, this predated my use of emulators, so I had no development environment to pay around. The problem was that NewtonOS can only handle left-to-right recognition and modding that, I would guess, is beyond my abilities.

(I've never played with the Japanese support. But it's still left-to-right. Right?)