--To write a novel version of Vingt mille lieues sous les mers, but from Nemo's POV.
It isn't like there isn't
precedent for this sort of thing, after all. Nor as though Verne himself didn't engage in meta-textuality regarding that novel itself, casting it as a published - and therefore subject to editing errors as well as unreliable narration - work of non-fiction existing within the "real" (secondary) world in which both the Monitor and the Nautilus existed, the same way that Watson's published accounts exist, and are self-referenced, within the Sherlock Holmes canon.
(The title, of course, should be Mobilis in Mobile - or, possibly, just N.)