I don't have a Cybook yet, but why don't you just upload an asian font and text for anyone with a Cybook to test?
I know of one limitation: text is only displayed from left-to-right so the usual (as far as I know) top-to-bottom then right-to-left orientation won't work (yet).
As for comics: they're planning to add the possibility to read from ZIP-files, so what you're asking for should be possible in the future. For now you can convert your comics to PDF, if you're using Windows with
Manga2Ebook and I've made a script for Linux that does more or less the same thing -- if you want it, just ask.