Warning: This solution requires you to lose all of your profiles and saved games. The file that stores your personal FOV settings is compiled and only readable with a hex editor. If anyone wants to try to figure out how to edit the FOV settings in the file, the file is located in <gamedir>\save, and it is the name of your profile with the .pro extension. I've tried to figure it out myself, but the FOV is an eight digit floating point number, and I have no clue how that gets translated to hex.
First, go to <gamedir>\save, and delete everything. Do not back up anything, just lose it all. Now go to <gamedir>\system. Right click on the file DefUser.ini, right click, properties, make sure "Read-only" is unchecked. Now edit it, and find these lines:
Change them to set your FOV. I recommend 95 for 16:10 displays and 100 for 16:9 displays.
Now save and close, and edit xiii.ini. Find these lines:
Change them to set your resolution.
Now launch the game, and create a profile. Your FOV settings will be applied.
The game's aspect ratio automatically matches your resolution. But the wider your aspect ratio, the higher the FOV needs to be to maintain Hor+.