About the REAL topic - I don't know too much about the variations in non-english alphabets, but maybe one of the non-english speaking versions sierra made does have other special chars, and you could learn from the way they implemented it how to make yourself a nice finnish alphabet in SCI.
Unless one is willing to sacrifice a few characters from low-ASCII, it can't be done.
Sierra themselves never sold a translated game made in SCI0. The first one that I know of
(and have had a chance to look at) is a German Space Quest 3. The original is SCI0, the translation
is SCI01. Since Brian isn't going to, I'd volunteer to code the support myself
(we don't really have to support the whole thing), but I don't have a suitable build environment.
I have written a detailed description of how multilanguage support is done in SCI01 which I intended
for the FreeSCI docs, but Christoph hasn't had the time to upload it yet.