The implications of the dog being real are much more interesting.
Babby Ford said that he heard a voice telling him to kill the dog because the dog was "made" just to kill, and therefore to essentially put it out of its misery. Now, we know hosts aren't created to kill. In fact, they're created specifically not to kill. Therefore, Arnold in the Shell's comments only make sense if the dog is (more like was amirite) real.
If that's the case, that scene is the most important one yet. Arnold was making a comment on life in general: all living beings are destined to kill each other and should be put out of their misery to avoid inevitable violence. This leads to several conclusions, both figuratively and in terms of narrative.
Specifically, it is clear that the park is a manifestation of humanity's obsession with violence. A place where the human id can run wild. The dog is a metaphor for Arnold's ultimate goal; wipe out humans to make way for the master race. The dog was the first casualty in the AI war against biological life, in order to eliminate the id entirely.
Originally, the aim of the park was to create an outlet for humans to express their violent tendencies, and id in general, against robotic beings, rather than express violence towards other humans. But ironically, the creation of those robotic beings revealed a better possibility, a future where there is no need for Westworld at all. In that future, the human id and the biological impulse towards violence has been eliminated.
Presumably, this is what Arnold envisioned. He may have killed himself and transferred his consciousness to either Bernard or (more likely) Ford in order to remove his own id and manipulate events at the park to make his vision of a more peaceful future--after a relatively brief interlude of war--possible.