I agree with the sentiments about supporting/recommending as few
character sets as we can get away with. ISO 10646 is not a standard
yet; it is only DIS; and as it stands it probably will not pass.
Recently there has been a break through on combining the best features
of Unicode and ISO-10646 that seems to be acceptible to both parties.
Only the future will tell. Assuming something like their roadmap
happens, there will still be various compaction modes and those may
have to be annouced outside the character set. Thus ISO-10646 by
itself is unlikely to be the right string.