Yeah, that could do it, a Discordant and Blank saboteur team directed to key targets by a Psyker cabal, Van Zandt's main divergence from the Dogmatic norm is that they're willing to make full use of even otherwise ostracized clades like Psykers rather than just hating them because the Emperor had a temper tantrum and never rescinded his universal death sentence before he was on the Throne.
You can't observe them through cameras, you can't observe them through postcognition, and you can send them precisely where they can cause the most damage. It's fully within the Imperium's power to produce these, especially if your population is at the point that it's at, and even just making it a priority to catch, recruit, and train these as agents as a matter of policy will massively increase their life expectancy, rather than just "If you see them, give your priceless asset a T-Shirt and use them as a human shield, if they die, you still win"