I love Belldandy's idea

. That sounds excellent.
I also tend to agree with Rei about the categories, etc. Perhaps a good compromise would be to create a base category list that should survive from year to year, with the option each year to add new categories. Each set of organizers is then free run polls and host discussion on what additional categories to include that year (and these would not necessarily be added to the base list -- that would be up to each set of organizers if they want to re-use categories from prior years). If the general consensus is to keep a category, then perhaps it should be included in the base list at that point.
As for the rilezu and repros -- this seems to be something that does change from year to year, and I do think that for the time being, the board should be polled on inclusion (and how to include) these types of artwork. Feelings and opinions do change over time, and with the board membership constantly changing, it might be a good idea to check how the participants feel about these things on a yearly basis.

If a trend develops for repros & rilezu, then maybe inclusion into the "set in stone" rule set would be in order.