It would be neat to have a currency that was firmly pegged to ICPI, it would at the very least provide a good testing ground to determine whether some of Nash's predictions are correct. However, one problem that I don't see addressed in Nash's work (at least the papers that I've been able to find) is that of political uncertainty. No nation-state can give a meaningful guarantee that the currency will remain perfectly pegged to ICPI. Leadership and policies evolve over time. Even if we could formulate some philosophical basis for a perfectly calibrated ICPI, a currency can still collapse due to political instability in the sponsoring nation-state. It can even be manipulated by manipulating the commodities in the ICPI portfolio. This is a cool idea but far from perfect.