Perhaps, rather than one currency, a basket could be used. That way any strong moves could be absorbed, and often countered by the opposing movement of another currency. It wouldn't have to be complicated, as long as the basket was set and not adjusted further unless there was a major event. In that case, there could be a rule in place that drops a currency if it drops by more than XX% or rises more than XX%.
I don't know if that's a good solution or not... just tossing it on the table.