Well it’s not so much as swapping entire models themselves as it is modifying values, such as how much an item or skill affects player data.I tried modifying the .pak file myself (swapping NPC models), and the game doesn't work when I tried to run it using the modified .pak, then I tried to repack it without doing any changes and the game still doesn't work. It seems that repacking the .pak file outside of the Unreal Engine Editor causes the .uproject file in the .pak to be unreadable or something like that.