His initiatives thrived for about 50 years and have only been partially put down through a decades long, colossally expensive PR campaign conducted by the highest reaches of society. The constitution's simplicity makes it highly interpretive, as such I'm more interested in the current political and social climate and how it is formed by those with the means to do so. If I were asked how I would change things for the better, I would start by changing the control of the flow of information, not with a new constitution.

you are the media you consume.

It is conservative in that it doesn't specify a whole lot of things modern constitutions specify, as millman mentions. But is that really a problem? It has enough leeway to implement pretty much anything. Is there some specific social policy you consider unable to be implemented under the current US constitution?

There is also the fact that people will only accept so much change at a time -- as the population changes, the courts change too.

I disagree on this idea that the U.S. constitution is outdated. It has two points strongly in its favor.

First, it is a pretty solid document of the Enlightenment period. There are flaws, but the rights-of-man and the reason-versus-religion dimensions are good, and the overall structure of government is good (better than the parliamentary system by a long shot, in my opinion).

Second, it is a straightforward statement of values rather than a prescription of points of law. That simplicity is a big reason why it's been stable for so long.

Under the U.S. system you can have a conservative government or a liberal government, while retaining essential human rights in either case. There was plenty of pushback to FDR's proposals, and there is plenty of pushback to GWB's proposals. I think that the Constitution is one of the strong points of the U.S. system.

quasi-scientifically. Unlike the Federal Constitution, many state constitutions are easy to amend and, in many states, replace entirely. Alabama's constitution, for example, has been amended 770 times (!), and Georgia was the latest state to ratify a completely new document (in 1983).

Now, maybe I'm a little myopic (because New York has a really pathetic constitution), but I can't think of any state constitution that is demonstrably better than the stodgy old Federal Constitution. Yes, I'd like to see some changes (in particular an amendment guaranteeing freedom from religion), but all things considered, i think it's mostly evolved into a sensible, workable system.  

There was a lot about the dead-on-arrival EU constitution that I liked, mainly the parts about social and economic justice, but as a system of government it was, imho, far less democratic and progressive than what the U.S. has. And that, I'm afraid, is what would happen here as well; we'd trade a quirky but fairly workable system for a technocratic elite-dictated bureaucracy.