Joking aside, I was thinking of offering an asset like this. I even emailed nefario asking if it was OK to offer this kind of asset but he never contacted me back. I figured since he was going to install some kind of prediction market on GLBSE that my offering would be voided after that, which was my reason for contacting him. I see a slight problem with your asset but you can find out when I create my own

Clearly there are various ways to bet on or against Pirate. Predictions on the probability of a default in a given timeframe (which sounds like what you were trying to do) are certainly a possibility, but are too artificial. The currently offered Anti-Pirate bond, and the yet-to-exist publicly traded perpetual pass-through bond which pays weekly dividends, are commensurable with the underlying instrument of investing in BTCST.
But if you think there is something wrong with my offering, please do share.