Back to basics, government-wise: reorganize the Executive Branch according to Constitutional purposes

In the Preamble to the Constitution, the basic purposes of the United States of America are enumerated:

1. Form a more perfect Union
2. Establish Justice
3. Insure domestic Tranquility
4. Provide for the common defense
5. Promote the general Welfare
6. Secure the Blessings of Liberty to ourselves and our Posterity

So if I were President, I'd reorganize the Executive Branch to fit. Six Departments, or Ministries, or whatever you want to call them, with the appropriate agencies and bureaus rearranged accordingly. Functions that couldn't fit within this scheme would be kicked back to the states, unless we decided by Constitutional amendment that we wanted to add other purposes.

Of course, there would be some very interesting conversations that would have to go into this redesign - what do we mean by things like "more perfect Union" or "domestic Tranquility" or "general Welfare," anyway? But once we were done, we would know that whatever the Federal government was doing was indeed something that it is intended to be doing.