Thinking more about this concept of topical threads, one thing I don't want to lose is keeping sets together. It's thrilling to see all the naughtiness of one group of people in one place, and I will be the first to say I do not want to have to navigate multiple threads to see all the photos from a single set.
So, I'll make an exception to rule 5 in the OP: feel free to post images with nudity when they are posted as part of a set that includes non-nudes.