It would be possible to include some parts of the new documents in the prompt so you can answer questions about new facts in the style and tone of your old documents, which we feel is useful. We are also experimenting with adding Retrieval Augmented Generation alongside fine tuning to see if the results are better than either or.
disclaimer: I work on Helix
A financial product that is only available to iPhone users seems like a reasonable business, but if it's only available in one market it's limited and you can't build much else on top because it's slicing the market to granularly.
I realise that international financial products are hard, but isn't that the reason why Apple is delegating the finance part to Goldman Sachs (and I suppose, theoretically, others in other countries) – so that they don't need to deal with the nitty gritty in each region?