Interest rates have an interesting effect and I have been thinking a lot about it while traveling to/from Miami. Here are some of the thoughts I have had.
1) Price Fixing of any form will result in problems, thus 5% price fixing will result in the price of BitAssets diverging proportional to the difference with real world interest rates on the same asset.
2) Price Fixing at 0% is no different than price fixing at 5% in this regard. It would give you a perfect price *today* but without a proper yield there would be no demand to HOLD it thus create a lot of churn as people look to move to a higher yield on that asset outside the system.
3) BitUSD needs to be correlated to the price movement of USD, not pegged TO USD in a perfect 1:1 manner. Remember, there is no such thing as USD, just JPMorgan USD, BitStampUSD, BOA USD, FRN USD and each of these has a floating value against one another based upon the current interest rates offered at the various banks and the credit worthiness of each institution. So long as a 2x gain in FRN USD results in a 2x gain in BitUSD it doesn't matter if FRN to BitUSD have a slight premium or discount, this premium or discount will be a 'constant' and mostly stable offset driven by constant and mostly stable interest rate differences.
4) The interest rate on Gold, Silver, EUR, USD, etc must all be independent and adjustable to market conditions in order to achieve a more accurate peg. The way this can be achieved is by using one BitAsset as a prediction market on what the interest rate should be on another BitAsset.