This won't work, because those employees don't actually register as toxic for the company - au contraire: They have reached - and quite possibly exceeded - their predefined performance targets! They have done exactly what they were hired for. You have to realize that things like long-term quality, or even reducing total costs for the company (only the silo is important!) is not a performance target in this scenario, and that's the root of the problem.

It's a systemic problem, a problem of corporate structure and incentives, and exactly the ecosystem where these kinds of contractors thrive.