WWI simulation becomes available at the beginning of sequence 6 in the main storyline. This savefile is parked there. All you need is access to the portal; perks and skills are all pre-determined.

Savegame location is C:\Program Files (x86)\Ubisoft\Ubisoft Game Launcher\a whole bunch of numbers\1957

Rename to 1957 and replace the entire 1957 folder (or simply put the contents directly in the existing 1957 folder). This savegame also has the Jack the Ripper DLC unplayed.