It may be a good idea to change Rule #3 so that it doesn’t include “furry” so much, such as:
“If an image includes an anthropomorphic character that is not specifically pony-related, tag this as “furry”. A major part of the image must be pony-related in order to be allowed (see Rule #4). Species such as diamond dogs, zebras, changelings, etc. already featured in the show are fine.”
It may also be a good idea to not even let the “furry only” tag exist because people will only continue to get all up in arms about things. Rules need to be clarified well enough to dissuade furries from saying “oh! another booru I can post whatever I want to as long as I tag it as “furry”!” (especially if Zizzy and friends are already doing a furry booru) and to give other users confidence that the place will not be infested with furry images.
Otherwise, this place will be DOA unfortunately.