The time required of/for/by workers to move from one job to another -all correct, it depends on who initiated the act. Was it initiated by the workers or someone else?- Another attempt of/for/by the West to impose their cultural values on us. *-same rule applies*-

The time required for the workers to move from one job to another. - This sounds most correct to me. X is required FOR the actor TO do something. Another attempt by the West to impose their cultural values on us. - Something is done BY an actor TO achieve a desired result. I hope my attempt at explaining this was clear.