It could also make sense to have a few different categories for different kinds of fics, like one-shots versus longer works, AUs and crossovers, and shippy and non-shippy fics. That way, more people and fics could get recognized.
I had plans for that too. Here's what I was thinking:
By character: One category for each member of the main crew, plus an "Other" category
By relationship: Gen, het, M/M, F/F, and Emil/Lalli is so popular it could plausibly get its own.
By genre: Action/adventure, angst, fluff, horror, humor, crack, hurt/comfort, tearjerker (romance is already covered by the relationships category)
By setting: Canon compliant, Y0/prologue era, pre-mission, post-mission, Dreamworld, Alternate Universe, Alternate Reality, crossover
By format: Oneshot, WIP, best (multi-chapter) work completed this year, best series