What I've wanted to do for a long time is implement UIA with custom feed authority. Let anyone register a market-based UIA and let the issuer specify a feed authority, an account or set of accounts that can set the feed value. Shorts and longs then bet against each other on the feed. Then have a process for transitioning that to a delegate-based feed when the market is big enough.
Don't forget to allow setting a custom margin call limit too! (And get rid of the initial collateral requirement.) Let people choose what level of black swan risk they want to tolerate (at the cost of lower leverage for shorts which means less short interest, if any, will be offered and a more difficult time to obtain the assets in the first place).
Also, separate out the price feed authority from the BitAsset. I want to be able to create multiple BitAssets that can use the same feed authority. In fact, I want to be able to mathematically combine the median feeds from various feed authorities. For example, imagine a feed authority publishing the USD/BTS price and another publishing the Gold/USD price. I want to be able to make a BitAsset that multiplies the median price feeds from those two feeds together to create a BitGold variant that might have a higher margin call limit like 300%.
Also, allow the BitAsset to specify the asset type that acts as the collateral. I would like to create a BitEUR variant that sets the feed to a EUR/USD price feed from some feed authority, set the collateral asset as BitUSD, and the margin call limit as 105%. This might be an interesting asset for currency traders who want high leverage.
Further discussion of this proposal here