Yeah, you really need some specialized interface that encapsulates all the things you may need from your string processing, but can spit out a representation of that string in various encodings.

In line with the spirit of this article, that interface should use UTF-8 storage internally as well, but this should be transparent to the programmer anyway. Dealing with encoded strings directly is a recipe for heartache unless you're actually writing such a library.

A higher level language, honestly. Perl, Ruby, Python3 and Haskell have excellent crossplatform utf8 support, and I'd be amazed if OCaml didn't. But if you want to write C++ code that works on windows, you're in for some pain.