The Defense of the nation is one of the things the Constitution specifically provided for.
Department of Energy should mostly go, but there is a part of that related to what was the AEC that must stay in some agency. It is weapons related.
I believe the VA has it’s place.
The nature of the post office has changed radically. but it should still exist in some form.
But you have the right idea.
We have a DoD for all of that. The Air Force doesn’t have a job right now. The idiots are trying to kill the A-10.