It wouldn't matter where it was, just so long as it was accessible to anybody. Legally, this exchange would only be trading in crypto-tokens.... Like Cryptsy or coined up.
When bitUSD is ready, it should be used in a scenario like this, It would really help adoption if people were able to see it out there solving actual problems. Generating freedoms. Proving it's metal so to speak.
We just need multiple on/off ramps. that's the trick tho, the capital flow needs to touch the banks somewhere. The instant it does, it generates liabilities for whoever handles it.