FOREX is a fairly small part of the four Australian banks' derivatives, and I'd be surprised if the CHF was a big component of that. Interest swaps comprise their biggest derivatives by a long way.
But if the trade is too loss-making well, the bank can just change the trade. Easy way out.
And that is probably what would happen if a series of interest rates sparked a derivative crisis. The authorities would cancel them, leaving the smaller banks to take the charges on the nose, causing them to fail and the depositors to bail into the rescue. Been done before. Will happen again.
