It's really a non-Roll20 question. You might get more answers by asking this on another Roleplaying oriented forum, such as, for example Reddit or <a href="http://www.RPG.net" rel="nofollow">www.RPG.net</a> Sounds like a fun campaign! There is not an "official" RPG for Avatar Airbender yet, as far as I know. It would be a homebrew based in some other game system. My answer would be No, do not have a Player as the Avatar if you have a group of players. EDIT: But rather than posting a whole discussion about that subject here since this board is meant for Roll20 questions, I'm just going to PM you directly regarding Avatar gameplay.