Well if AIXI believes that its interactions with the physical world are only due to the existence of BRAIN, it might not model the destruction of BRAIN leading to the destruction of its input, output and work streams (though in some sense this doesn’t actually happen since these are idealized concepts anyway), but it does model it as causing its output stream to no longer be able to affect its input stream, which seems like enough reason to be careful about making modifications.
Well if AIXI believes that its interactions with the physical world are only due to the existence of BRAIN, it might not model the destruction of BRAIN leading to the destruction of its input, output and work streams (though in some sense this doesn’t actually happen since these are idealized concepts anyway), but it does model it as causing its output stream to no longer be able to affect its input stream, which seems like enough reason to be careful about making modifications.