As a first step in this direction at some point in the future I'd like to start an Australian cryptocoin that is pegged to the Aussie Dollar. You'd be compromising many of the values inherent in Bitcoin, and introducing central points of failure, but properly managed it would be a powerful force, especially if AUD -> AussieCoin is easy, then you can cheaply, quickly and easily change AussieCoin for Bitcoin without any restrictions.
Right - I guess the main point of failure / excessive trust that you're stuck with is that you need a reliable way to know your own exchange rate. Once you've got that, in theory it should be possible to do the rest just with algorithms in the software, eg. people can volunteer to destroy coins if the exchange rate is too weak, and get rewarded with the ability to print them when the exchange rate is too strong.
For that element of trust, I guess you'd just have a list of trusted public keys in the client for people who could be relied on to give accurate information about the exchange rate for a fee, and the community would have to police that list if anybody got caught misbehaving.
One hard thing about boot-strapping this is that the currency can't work without reasonably liquid exchanges, and you can't create liquid exchanges without an established currency. But once somebody comes up with a nice, open system allowing you to trade Bitcoins for AussieCoins (etc etc) you could then piggy-back off publicly available data about the Bitcoin exchange rates. I think you could design this so that the system could survive not being confident about the exchange rate all the time - you just need to know that any sustained deviation from 1 AussieCoin == 1 AUD will eventually be corrected by printing or destroying money, at which point you should be able to rely on speculators to keep the price in line.