In general, one of the best reforms I can think of would be to return most of the Departments to agencies in the Department of the Interior, forcing them all to become one level of organization smaller.
The ATF, however, should be further restricted to being a division of the Bureau of Indian Affairs, and only have jurisdiction in Indian Country and federal lands.
How about we just do away with the BATF altogether and let regular treasury agents deal with what they are supposed to be doing?
Federal anything is not readily accepted on Indian Reservations.
ATF sould be disbanded and many of its current and former employees should be in prison.