St Naz + Schleuse is not
required but is a great enhancement/add on for GWX consolidated by a number of the GWX Team after GWX 3 release.
I thoroughly recommend it as it adds some new units, St Nazaire harbour and a few other highly desirable mods to the core GWX 3.
Further details and the St Naz + Schleuse mod is at:
http://www.subsim.com/radioroom/show...light=schleuse