I think that's really cool. I've played around with doing RAG with some works of fiction (e.g. the works of Shakespeare, every 40k novel) with the goal of making an index that could be natural-language queryable. For instance, you could look up "How many times does tolkien mention how tall the grass is in a scene?" and get a correct-ish answer (if it worked properly, which mine... didn't).
I think if they could be made to be properly deterministic, it would be possible to catalogue a sample of prompts each version gets "right" and prompts it gets "wrong". This wouldn't necessarily be a good "correctness score" but it would give an idea of the types of flaws present in the model that would help in finessing the next version.
That's basically where I got stuck, but this was a while ago so maybe the situation has changed in the last few years. I'm curious to hear how you are dealing with nondeterministic effects as well as... I guess systemic wrongness, where some bias in the model training just makes it pretty consistently wrong on some answers.
I think if made correctly, such tools could be really useful in all kinds of settings.