There's no problem when you send a FS request (open,stat etc)-- this can easily be automatic. There's a problem when you receive FS info, that is, OS cannot decide for you what format to provide data in. For example, on win32 you might not want to have results in unicode, -- so OS conveniently maps internal UTF16LE names into, say, Latin-2. Of course, if we (suppose) never use 8-bit OS interface, but only unicode API, we convert utf8<->bytes by using perl's Encode, but then another problem arises: other users of the OS may (externally) supply us with a 8-bit file name, and if system codepage is tricky, then there's no way we can correctly convert the supplied 8-bit filename into proper UTF8 using Encode.

I actually just 20 minutes ago send a mail to p5p with a proposed patch that does exactly this.