• go into C:\Users<username>\AppData\Roaming\Blender Foundation\Blender\2.79\scripts\addons
• extract the 'io_scene_ffxv_fbx' folder from the zip.
• restart blender if already open.
• In the user settings under the addons tab, disable the original "Import-Export: FBX format" addon, and turn on the "Import-Export: FFXV upgraded FBX format" addon.

When exporting to FBX, now a 3rd Version is available under the 'Export FBX' options in the bottom left: FFXV FBX.

Author: Wim De Clercq Credit to Leon Blade for the diffuse value changes. https://gist.github.com/LeonBlade