When we founded Kraken, I did a lot of research and reach-out in the alternate financial systems space. The 'basket of commodities' suggestion is very well promoted by theorists in that area, though of course it doesn't remove the problem of manipulation: whether static or dynamic in composition, it has the same problem as setting central bank interest rates today - prior knowledge of manual change to the system becomes profitable, and corruption ensues. Some also suggest emphasizing particular qualities in the selected commodities.