@Mark – thanks for commenting, really useful.

You’re absolutely right – the fact that data needs to have a certain shape (and also the fact that the data needs to be exposed on-page at all!) is to a certain extent a downside of the proposed approach. Also it is probably the case that in reality a fair amount of munging will be required of extracted data. I guess a real-world test is the only way of finding out if this is enough of a barrier to make the idea a no-go or not…