It's not like trading stock pairs. All currency trades involve a pair. For example, if you buy Euros with $, you're going long the Euro and short the $.
If by currency pairs you mean buy Euros with $ and sell Swiss Francs for $, it's still not a pairs trade since there's a cross trade between Euros and Swiss Francs. So you can just cut down on the commissions by buying/selling the cross trade using futures. An in the end, it's just a currency trade.
