I have recycled the parts of my brain I used to store Oracle knowledge. Even then, I don't think I ever worked with non-standard character sets in it - only ASCII and some Oracle version of unicode.
My suggestion would be to do any transformations in tcl, rather than in Oracle. In fact I would suggest getting rid of Oracle and switch to Postgres. We did, and I haven't had a single moment of regret.
/Nis
