Hello everybody:

I've made a solution to "partial" solve Chinese display problem on E-ink.
As my description before, I was bothered by save webpage to epub and has all "?????" on the E-ink screen.
Thanks for seagal's advice, I can simply change the xml:lang from "en" to "zh-TW" or "zh-CN"

Unfortunately, we must unzip + modify contents + repack in order to achieve this goal.
I wrote a simple application on eDGe, try to do all these things automatically.
Here are the steps:

1. Open the browser and save webpages you want.
2. Open the app "epubeDGe"
3. Key in the folder path of the epub you want to convert (the default path is "/sdcard/public/web-epaper_docs/")
4. Key in the language you want . It will convert from "en" to what you want. ex: zh-CN or zh-TW. zh-CN get thicker font and zh-TW get thinner.
5. Press Convert! button and wait for a while.
6. After converted, It will show "File convert finished."

Please noticed that every time we choose the function of save webpage to epub is accompanied with open it.
In order to load converted epub, you must open another epub and reload your converted epub.
Now~ we all have correct Chinese epub display on the E-ink screen.

I just test it on my own pocket eDGe and use Chinese encoding webpage for test.
Maybe it might works on other language, let's give it a try.
Please let me know if this small app has any way to improve or report for bugs.

Here is the link of app:
http://www.gmart-web.com/epubeDGe.zip

Thanks!