There is a big thing on the wikipedia-l about writing up Chinese. One thing I gleaned from this discussion is that zh-tw and zh-cn are used to indicate respectively traditional and simplified Chinese. As it is relevant to wiktionary to have both correct spellings, I propose to use these codes as well as the zh code to indicate Chinese words.
I hope someone has a good suggestion for Serbian, cyrillic and alphabetic. There are more language that are written in different charactersets. I am looking forward to suggestions.
Thanks, GerardM