I mentioned earlier that I've submitted a draft SRFI about changes and
extensions to R5RS to make Scheme extended-character-set-friendly
(Unicode-friendly in particular).

I've drafted two additional proposals for:

~ Specifications for what happens if Unicode codepoints are,
  indeed representable as CHAR? values.

~ Specifications for identifier syntax and meaning if identifiers
  can be written using non-ASCII, Unicode characters.

These can be found at:

  http://regexps.srparish.net/srfi-drafts/INDEX.html

which contains:

* "Permitting and Supporting Extended Character Sets":
   basic changes needed to R5RS to make Unicode-based Schemes
   practical and conformant.

* "Scheme Characters as (Extended) Unicode Codepoints":
   Defining the CHAR? type to be a superset of Unicode codepoints.

* "Unicode Identifiers":
  Internationalizing the Scheme Programming Language.

  Note: "Unicode Identifiers" is the roughest of the three documents
  and I'm certain I could use some help with it.

It also contains some other string-related documents which aren't
Unicode-specific but which do make proposals that would interact with
both Unicode characters and strings and FFIs.

-t