If anyone is interested, I (long ago) found another: switch the current
codepage to an ISO-codepage!
There's a freeware package by Kosta Kostis for (plain-) DOS and it
works great here, though I cannot say anything about its functionality
in a dos-box in os/2 or win. It also comprises a keyboard-TSR to map
your typed characters to show up correctly when a non-IBM codepage is
active.
Additionally I wrote a 4dos-batch to be able switch easily between the
different charsets from ISO-8859-1 up to 8859-10, comprising greek,
cyrillic (ISO), arabic, hebrew among the other latin charsets.
You may of course also call this batch when needed by the pipe command
or in the shell ("!").
The main advantage of this approach is in my opinion that you don't have
to map any characters and just let them as they are, future apt readers
may eventually care for the correct display of saved messages of this
kind.
Thilo