1 gameplay wise
At day he should mostly be in the forest and not really interfering with the player but when it turns night he should become more aggressive and start to stalk the player and to sneak up on you like he did in hello guest along with maybe using items to use against the player like in 1.5 Also a cool side quest maybe even a main quest would be to try to take pictures of the guest after retrieving the camera
2 story wise
He should be the true hidden main antagonist like the alphas and beta and even the full game poster implied also you should Have him be the final boss of the game.
