I actually had the notion of Reza as Peats in the ridiculous plot twists thread...but Peats (if he can be trusted) has Reza's memories. So even if it's not his natural character, with enough motivation, a good actor could play the role.
There are a lot of possibilities with Reza
1) Peats was lying and Reza was not destroyed as he implied. All we really know is he was at the Border House and there was blood on his shirt. It might not even be his blood.
2) Reza was destroyed by the Dream Machine but WATI chose to reconstruct him for whatever purpose. In this case, it might be possible for him to recover his original personality.
3. Reza was destroyed by the Dream Machine but has been replaced by an A.I. (or by Peats, I suppose). In this case Reza is truly gone.
I'm leaning toward #2. My feeling is that if WATI were really sure of Reza, they wouldn't need to be leaning on Dr. Roman. His reconstructed personality may be under some kind of conditioning, but they want to make sure it's holding. There's that bug in the apartment to think about, too.
Given the emphasis on whether Zoe ate the meal he prepared or not in Chapter 1, I'm still wondering if he might be drugging Zoe.