I don't think it's anything that elaborate, personally, and it bears mentioning that the other translations of the game clarified that the "dreamer" is a distinct entity of its own.
Fandaniel's musing about Emet-Selch "finding a way" to do something suggests Zenos was tampered with somehow, and given the latter's tendency towards random sentiment when confronted with the nostalgic, I'm still leaning towards Zenos bearing a familiar soul and having been given memories of the Final Days out of a desire for him to in some small capacity be the person he once was.
It would also be a bit of an ironic twist if that brief moment of whimsy ends up nearly damning the world as I'm getting the impression those dreams of the Final Days are playing into Fandaniel's scheme somehow. Having someone with constant nightmares control a "dreamer" that has countless people under its thrall could be a perfect way to recreate the circumstances that led to the Final Days in the first place.