This makes no sense at all - in order to peg NxtUSD to say NxtAUD *inside* the Asset Exchange would mean that the actual USD/AUD exchange rate has to be ignored (as that by definition is *outside* the AE).

So by definition you can't peg those currencies to each other in any meaningful way - you might decide you are going to always exchange 1 NxtUSD for 1 NxtAUD and the opposite but even that won't work unless you have exactly the same amount of either.