Updated Nov 2
Thanks for the A2A.
Generally, the assumption could be that, William is human in (almost) every scene before the S2 finale post-credits scene.
However, there may have been moments that appeared to be in the “present” timeline, but which were actually rewinds or fast-forwards. The arm-cutting incident was presented twice (before and after Dolores arrives), and might have been two different repetitions.
Related to this is the, “The Stain” speech, talking to his sleeping wife in The Vanishing Point. He is looking down and feeling his right arm, as if he thinks there is something inside.
Before he kills Emily, he says, “It was built in from the start”. Perhaps guests have some kind of device implanted into their bodies, to make the recordings of their actions, and gradually upload their consciousness algorithms to the System. This device may also have been what William used to communicate with the control room, requesting the exploding cigars during the jailbreak.
Next season, there will be a symbolic situation, as William’s shattered right hand is replaced with a robotic version.
Have you noticed that, we know the surnames of Logan and James Delos, Robert Ford, and Arnold Weber, but we have never heard William’s surname? Although this doesn’t necessarily mean anything, since some hosts have surnames, and others don’t.
We know almost nothing about William before his first visit to the park, except that he is from a poor background, probably excelled academically, and married into wealth.
So far (before the post-credits scene), human-to-host-conversions have never worked, and we have only seen it attempted with James Delos. The electronic copy of his consciousness cannot handle being loaded into a host body.
Bernard started as an attempt to resurrect Arnold, but only worked by making him into a different person, only partly based on Arnold. Although, in the S2 finale, Dolores introduces him to William as if he were actually Arnold.
William’s original plan included having his own consciousness uploaded to the System, to be electronically tested, then loaded into a physical host body, and he had aspirations of immortality, like James had. However, William has changed his mind, and is attempting to prevent this. Dolores talks about him wanting to fully destroy himself. He knows that, the System has already decided that humans are simple algorithms that will always have the same bad outcomes, without real choice. This is why, in the post-credits scene, he has the disappointed tone with, “I’m already in the thing, aren’t I?” Then, he says that, he was trying to prove that he really did have a choice, and gets a facial expression with an ironic smile, like he realises he was wrong.
There are other lines, like, “How many times have you tested me?” and also, “Again, and again, and again…” So he knows that he is the most recent in a long series of host-William attempts, which have either failed the fidelity interview, or which have played out repetitions of the same actions, particularly killing Emily.
Previous to this, he may have been tested electronically in the System, but now host-Emily states that, the System is long gone, and this isn’t a simulation (i.e. he is now in a physical host body).
In this scene, it is decades after the “present” timeline, after a war between hosts and humans. The human-William would probably be already dead of old age, at least. Maybe they are punishing all the former guests whose consciousness they possess, by forcing them to relive painful events, like the way that the hosts were looped into painful events. But maybe they are looking for some kind of information that they need.
Perhaps the hosts have conquered humanity, but are now locked into new repetitions and feel like they still don’t have choices(?) Perhaps they are looking to study William, and his ideas of making choices, since that was part of his motivation, going back to the S1 “No choice you ever made was your own. You have always been a prisoner” speech to Lawrence(?)
ETA: It just occurred to me that, in the post-credits scene, perhaps host-Emily also wants a replay, in which host-William makes different choices. Dolores mentioned “The gift of choice” between herself, Arnold, and Bernard. Perhaps this is what will be offered to host-William? Either because the hosts need to have that different replay conducted by him, or perhaps just out of compassion towards her father?
I’ve seen some speculation/claims that, in the S2 finale, there is some back-and-forth timeline switching between human-Hale and Halores. Perhaps this is also shown with William.
Also, there was a very brief glimpse of a rather pissed-off looking William – probably a host-William – sitting in a room at The Mesa, during the general commotion of the uprising.
My guess is that there were host-William attempts being conducted during the “present” timeline, while human-William is still alive.
An interesting point is the S2 “Do you believe in God?” scene with William and Lawrence. Then, William said that, he felt that, he had already been judged. As if, by that point, the System had already told him that he was a hopelessly evil person, doomed to repeat his bad behaviour. And that, he was going to aggressively appeal that verdict.
We know that he is already feeling guilty for Juliet’s death, and her reaction to seeing the recordings of his actions in the park. And is also contemplating his evil attack on Maeve and her daughter. But perhaps this is some kind of host-William attempting to repeat things, and show that, he can choose a different path(?)