Perhaps they should restrict these sensitive positions to full timers who have committed to the Agency -- i.e. they know that the organization will be watching them pretty much for the rest of their lives. Ex-agency people I've met said they have to notify the Agency whenever they travel abroad -- if they don't hear back, it's fine, but the Agency reserves the right to stop them.
The amount of damage (some might prefer to say, whistle blowing) done by contractors in recent years suggests that it's time to reexamine who gets such sensitive access.