The document was specifically, and explicitly, designed to maintain the protections of American citizens. Chattel were not citizens. So you can't claim that it was designed to limit the freedoms of people under it's protection. Further, you also can't claim that the Constitution, in its initial form, was inherently supportive of slavery since a portion of its drafters were active Abolitionists, and even the ones who weren't had all contributed to the Abolition movement by the end of their reigns. It wasn't Americans in general that introduced, or even endorsed, the practice of slavery. At any given time, the portion of Americans that adopted slavery as a practice was tiny.
Similarly, the implicit claim that women weren't protected as citizens under the Constitution by token of lacking the ability to vote is tangent to its underlying purpose. There was nothing in it that explicitly stated that women should or should not have been allowed to vote or even work. Females in politics and/or the work place had always been a policy issue, and not an issue of constitutional principles, but that's an entirely different discussion.
The inclusion of amendments after the initial draft was designed to reinforce the principles already established and delineated to the document in its previous form without adding any principles of its own. To profess that it should be "changed" as a principle unto itself demonstrates contempt for its very conception.
The horrible truth here is that principally changing the Constitution in the ways that you espouse (see also: Fourteenth Amendment) has only served to socially engineer the people on the bottom from the top tiers of government, and has not reflected any cultural shifts that began with the people themselves. Thus, any further lawmaking or right-forging have been acts ordained by the politicians seeking to change the culture from positions of power, rather than the will of the people seeking change itself. It's oligarchical serfdom all over again in the form of bureaucracy.
