Does anyone know if it is possible?
Yes it is. Did it yesterday on windows 10, but with the Steam version. Not sure if it will work for the GOG version.
I figured it out. I run Windows 10, use DxWnd, make sure Legacy mode is supported in Windows (see here: https://www.reddit.com/r/ffxi/comments/3ly0dz/windows_10_with_windower
/) and use these settings: https://simfileshare.net/download/1006218
/ which you can import into DxWnd.