Asian Experience
There is at least one Asian carrier that route endorsees individuals on one route and then requires the person to fly that route for a period of time. Two years comes to mind however this is subject to correction.
Having an individual intimately familiar with a specific route provides defenses that are missing with less familiarity.
A casual knowledge of many routes does not equate to an intimate general knowledge.
Forcing individuals to operate to ports that they would normally choose to avoid like for example JFK during the winter, has significant risk management issues. Knowing ones own comfort levels and operating within those levels is better risk management than when the same individual is working at the top end of his comfort zone where there is less margin to deal with non normal occurrences.
In the inevitable accident/incident occurrence that will result from this new policy a functional investigatory agency may well find that the author of the policy is a significant factor.