Idea for short story:

• In the future, people can upload themselves to the cloud.
• The process is both incremental and definitive.
  • You can help train your doppelganger first: like in the Caramel City short story, for example, or by otherwise contributing training data for models.
  • You can also go through a one-time process which scans your neural connections and tries to decode them/encode them in extra models. Or tries to find an "embedding"; a lower dimensionality representation that can be interpreted and mapped to the existing models. But the process is destructive.
• People are aware of this tradeoff, and must decide for themselves when to undergo the destructive process, if ever. If one postpones it too much, natural death will eventually happen, so there's a risk.
• Different people give different credence to the resulting simulations. For most it seems clear that with little training data the models are clearly inferior in awareness and richness to a "real person", but as models get better (due to both more training data and better technology)

Aside: perhaps Caramel City should be part of this, and this has the potential to become a novel or at least a tight collection of short stories in the same world. Perhaps Caramel City is how it starts; eventually a coworker in that office dies, and people learn to like having the Doppelgänger still around. Because of this eventually they muster the courage to tell him/her what has happened, and what the truth is; but then the Doppelgänger surprises them by seeming to understand and reassuring them that no, it is OK, he/she is alive and knows that the people that he interacts with (who are partly also simulations) are alive too.

One interesting thing to explore in such a story would be the nature of the protagonist, of course. It could be that at some point the protagonist switches over to their Doppelgänger, and perhaps at some point realizes this, but decides that it doesn't matter; or ends up in anguish about the possible differences between themselves and the "real" them.

Before that and on a larger scale, a world with these rules would offer an opportunity to explore matters such as the nature of the self. Each person would probably have a different threshold for how good a model would need to be to consider it equivalent to one. Some people would require perfection, or just opt out of the process altogether due to personal conviction in the uniqueness of human consciousness; some people would reach that conclusion that, actually, perhaps being 80% or 90% similar is enough to identify with the Doppelgänger and want "it" to live on. One forgets constantly, and actually changes significantly over the course of most multi-years periods; some theories of consciousness probably call this (check?) the illusion of permanence. Or actually perhaps it's Buddhism. But they are in some way alike.