FFDB - SDE

So. I was thinking of building a static database editor (a thingy that helps manage the non-dynamic or at least less-dynamic parts of the site, like characters, ships, that sort of thing) and I've immediately encountered problems:

1. Characters. Should all characters that appear in canon be listed? Or only those that are actually used as main characters in a listed fic, and so the list of characters grows with the list of fics? While you're thinking about it, consider original characters – should they be listed as individuals or grouped together under “OFC”? Having individual items for them makes fic descriptions more expressive, but also makes a thing like “Snape/OFC” harder to make, and that is after all very close to the system's requirements. So, how do we treat Ms' Moody, Loomis, Green (remember her?) and all their friends?
2. Genres. Since I'm basing the thing in part on IMDB, I've looked at their page. What they're doing with this metadata is inspiring. But, what are the genres of Harry Potter fan fiction? Are they the same as for general fiction? Which are...?

I really need to hear what you have to say.