Huh. Just tested it, it straight up doesn't work. I think the game might have been updated. The difference in versions between the launcher and the game data could be preventing the game from launching.
I'm sorry to say that I don't feel particularly inclined to update the mod right now (maybe ask again after Chapter 3 is released). That said, if you REALLY want to play the game with Ralsei holding a gun, you could try manually patching the sprites into the game.