“There are no good agents. Just end the Bureau.”
The Director is an appointee; his assistants may be as well. But the rest are civil service employees. The President can remove a civil service person if there is proof that they’ve committed a crime but he can’t summarily fire the entire rank of employees.
They may not be able to be fired, but I could clear the entire DC head quarters by reassigning every member to another field office with order to report to their new place on Monday. If they object the stock answer is "Your resignation has been accepted". Pick their new duty stations out of a Hat that just happens to not include NYC.