Gibney isn't the first to suggest this. Obviously, PMC's themselves have always suggested this. Still a good idea. Maybe a better idea now than it was when Executive Outcomes was suggesting it for Rwanda (prior to the great machete party) - Today's contenders seem to offer more stability, and despite the media's efforts less mercenary stigma.
From the Atlantic piece:
"There is a different, more robust approach to making peace in nasty places: deploy private military companies like Executive Outcomes, whose small, highly trained force defeated insurgencies in Sierra Leone and Angola during the 1990s. Executive Outcomes is now out of business. But as researchers like Peter Singer have documented, the private-military-company marketplace now fields scores of firms (including the U.S. giants Xe—formerly Blackwater—and DynCorp) that take in billions in revenue. Put them on retainer, and they’ll go where they’re paid to go—unlike every one of the 19 countries that had pledged troops on a standby basis for UN peacekeeping and then refused, in 1994, to send them to Rwanda."