So even when you talk about amplifying f, you mean a certain way of extending human predictions to more complicated background information (e.g. via breaking down Z into chunks and then using copies of f that have been trained on smaller Z), not fine-tuning f to make better predictions.
That’s right, f is either imitating a human, or it’s trained by iterated amplification / debate—in any case the loss function is defined by the human. In no case is f optimized to make good predictions about the underlying data.
My impression is that your hope is that if Z and f start out human-like, then this is like specifying the “programming language” of a universal prior, so that search for highly-predictive Z, decoded through f, will give something that uses human concepts in predicting the world.
Z should always be a human-readable (or amplified-human-readable) latent; it will necessarily remain human-readable because it has no purpose other than to help a human make predictions. f is going to remain human-like because it’s predicting what the human would say (or what the human-consulting-f would say etc.).
The amplified human is like the programming language of the universal prior, Z is like the program that is chosen (or slightly more precisely: Z is like a distribution over programs, described in a human-comprehensible way) and f is an efficient distillation of the intractable ideal.