A lot of people seem to like the Black Fox idea so far, though some have had reservations--many of which I share. I'll cover these in another post. But for now, I'm letting my imagination run away with the idea, though I've certainly not committed to it yet.
The codex item in DA:O is pretty obviously loosely based on the adventures of Robin Hood. My imagination is a very feeble thing, at least as far as making things up out of thin air goes--if it has any strength it is associative and adaptive. Accordingly I decided I ought to look into the Robin Hood source material for a start; but what *is* Robin Hood source material? I went to Barnes & Noble to look around, but the only things they had were in the children's literature section--so I looked there, because something's better than nothing. (The guy who helped me also told me there's
another Robin Hood movie coming out? With Russell Crowe?) I came across
The Adventures of Robin Hood by Roger Lancelyn Green, which suited me just fine.

For one, it may have been intended for the adolescents of 1956, when it was published, but the note by the author which serves as introduction is better reading for literature nerds like me:
My first four chapters show perhaps the most varied example of this method of literary mosaic. Chapters 5 to 15 follow almost entirely the Lyttel Geste and the Ballads, but with selection and a certain amount of conflation and regrouping. Chapter 16 uses two scenes of George-a-Greene; Chapter 17 combines a ballad with a chapter of Peacock; Chapter 18 is based on The Sad Shepherd (but with my own ending, since that made by F. G. Waldron in the eighteenth century seemed inadequate; the final song alone is Waldron's); Chapter 19 combines two ballads...[etc., etc.]
Anyway, it seems that Robin Hood itself is a heterogeneous mix of tales--there really is no single work which serves as its source. I think I'll play with this, in some way, if I end up doing a Black Fox mod. For one thing, I'm almost entirely convinced now that the mod would have to be a string of individual episodes. This is not only easier to do from a technical standpoint--shorter mods = shorter development time = less risk of burnout--but the episodic nature of the adventures of Robin Hood/the Black Fox also make it a no-brainer.