El Cid: This sounds logical, but the converse is true too. Don't join a pond if you know your time is up and you're not going to renew your membership.

Both your idea and the way it is actually done here are fair, though one may not seem right to the person that becomes a Pawn after starting in a pond. I can't remember if it clearly states in the rules as to what happens to you if a pond continues pass the expiration date of your paid membership.