I understand you meant this for Travelin Dave, but allow me to answer, so that you can fully get my position.
Yes, I believe that there should be structures outside the executive branch that impose limits upon what the executive branch does with the resources that the executive branch controls. I always assumed this was part of the checks and balances our forefathers intended. But I'm sure you know the old adage about assuming.
Well, there is an open question about the separation of powers and the powers of the chief executive, which the SCOTUS is likely to settle this term as it reconsiders Humphrey's Executor v United States.  But the monuments in Washington DC are under the auspices of the National Park Service, which is an executive branch agency, and the White House itself is also under the auspices of the Committee to Preserve the White House (which was created by an executive order of LBJ) and the Capitol Planning Commission, which was enabled by an act of Congress, but is also an executive branch agency populated by presidential appointees.  
Followup question: Does it disturb you to learn that in 2009 Barack Obama, with private funding, installed basketball hoops and markings on Dwight Eisenhower's tennis court, and didn't submit the plans to the National Capitol Planning Commission?  Or is that too minor a change to bother with?