This is what bitcoin is missing. You can have a cash settled futures market and use the fix protocol for market data and execution. Of course, you can also have options on those contracts. Preferably, it may even be decentralized similar to Bitcoin itself. The 'Colored Coins' concept looks pretty interesting: http://www.youtube.com/watch?v=fmFjmvwPGKU This way, a transaction tax would be null from the get-go, as people could simply use the bitcoin market. Furthermore, this would also give people incentive to actually hold their wealth in bitcoins in order to create a stable bitcoin economy.