If you go to
this thread, in the Sony Developer's forum, about the PRSPlus customised firmware for Sony models, then search the thread for "Chinese" you will get some hits. I know PRSPlus allows you to redefine fonts by 2 different methods because I use them both - only in English though, I'm afraid:
- Sony fonts used by LRF/TXT/RTF and
- the fonts used by EPUB
Method 1 may suit you. However, I suppose Chinese font files can be very large so there may be special considerations. It might be worth you raising your specific Chinese questions there to get advice from someone who already tried it.
kartu, the creator of PRSPlus, is usually very helpful answering questions.
Don't forget to also get confirmation whether the menus and book titles can be displayed in Chinese.