If imprinted birds were to be released, even if they were taught to hunt, there would be many problems. Most importantly, they would occupy a territory that would be used by breeding birds. If they got hungry, they would go to humans for food. Imagine having a BBQ in your back yard, and a bald eagle lands nearby, looking to be fed. At this point, due to hunger, it would be very aggressive posing a danger to both you and to the eagle.
Imprints also know nothing about territories.
If they flew into the territory of another bird of the same species, they would not understand the other bird's calls. This could lead to one or both of the birds being injured or killed. Predators are another problem. People pose a tremendous hazard to birds, yet imprints have no fear of humans. Unable to recognize other predators they would not have the necessary defensive precautions.