i) desire to use characters from multiple character sets in plain text
it clearly solves this problem (or at least 95% of the problem;
as Ohta-san would point out, this may cause kanji to be displayed
as Chinese -- this is a defect but its better than NOT seeing
the kanji at all.)
Why don't you try to fix the defect?
With ISO-2022-JP, we CAN SEE kanji (Japanese Han) without any defects
NOW.
Moreover, The unificattion problem is the correctness problem.
No Japanses plain text is written in Chinese Han.
In the long run, it's much better not to have any data at all than
having half correct (that is, wrong) data.
My experience in Plan 9 is that there was
no sudden jump to multi-lingual documents but an increase in the
use of diacritics and the like, and symbols (a real Smiley),
and a shift from using formatting constructs to get overstruck/
accented characters to just typing the characters in.
Then, there might be major defects in Plan 9. Our experience of
ISO-2022-JP was that everyone started to fully utilize it within
a few months.
Or, it might be true that the requirement of multi-lingual document
in US is low, in which case, you can continue to use ASCII, until
you really need multilinguality at that time, you need REAL
multi-lingual environment, NOT defective ISO 10646.
Masataka Ohta