Haven't you done a PvP game like this before?
Yes. In fact Camelot is based in many ways on Mythic's text online RPG Darkness Falls: The Crusade. This game has a three-Realm conflict based in an original fantasy setting. Camelot has used the lessons learned from this game, in creating a balanced PvP system. While DFC is not a graphical game, it contains all the non-visual elements that will exist in Camelot: an extensive guild system, character classes, races, and a huge database of objects and monsters.