I would like to move from p(La)TeX (which was a TeX system specifically tailored to Japanese in a pre-Unicode era) to Xe(La)TeX, and I'm having a problem.
In p(La)TeX, Japanese fonts are only used for non-ASCII characters, and ASCII characters are typeset in Computer Modern, or Times, etc just as in the standard TeX.
I would like to have something similar in Xe(La)TeX. In other words, I would like to have Xe(La)TeX to use different fonts depending on Unicode blocks, say CJK Unified Ideographs or Ethiopic or Cuneiform, see the list here.
Is it possible with XeLaTeX and fontspec? Or do I have to hack the source code of XeTeX to do this?
(A very similar question is asked here, but let me ask it here again, hoping that the situation changed in the last six months.)