This issue hasn't yet been picked up to be worked on.
I had a typo in my earlier sample; you could try -Dfile.encoding=UTF-8 as a JVM argument to the designer launcher and/or providing the file.encoding property as a wrapper.java.additional property in the ignition.conf file. If the problem is a file encoder being created with default platform encoding somewhere, that would force Java on Windows to use a 'better' charset, which might fix this issue.