The problem that I have with fee values is that the purchasing power with Bitcoin is not fixed - a passport created 3 years ago might have needed to burn 100's or 1000's of BTC to claim legitimacy; requiring any application to have some sort of exchange rate lookup as part of the passport application.
Since the identities would be marketable the value of the identities would be pegged to bitcoin value. this would only become a problem in the situation where you had used this identity to insure something and during the course of the transaction the value of btc fell enough to make the indentity worth less than the benifit to the other party of scamming you. So long as bitcoin didnt fall precipitously and you made sure to only contract with people who left some wiggle room between the value of the identity and the outstanding obligations tied to that identity it wouldn't be a problem. 25% buffer should keep you safe from anything < than a rapid %25 swing in the value of btc