there is most definitely a federal law against murder: US Code Title 18 Section 1111

Any lawyers here to clarify? I looked this up [1], and find a couple of interesting things. First, it specifies a death penalty for Murder 1st Degree -- but we all know that there are plenty of states (most?) in which you cannot be killed for this. So there's a contradiction. Also, see [2]

Nothing in this chapter shall be construed as precluding the application of State or local laws to the conduct proscribed by this chapter, nor shall anything in this chapter be construed as creating any substantive or procedural right enforceable by law by any party in any proceeding.

So my best guess is that this stuff is applicable to DC, national parks, etc., but not to the states.

What's to stop a state, say Alabama for hypothetical purposes, from testing out slavery again?

Ummm... maybe the 13th Amendment? Honestly, I think you're being intentionally obtuse here.

Who picks the best results? Certainly not the federal government under a Paul administration.

The people of each state, or their duly appointed representatives, of course.

Many supporters counter by stating that people can just move to another state... but unfortunately for the poor moving is almost impossible.

This creates a competitive situation between states. In the end, the most prosperous states will be those that can find the best equilibrium between positive and negative rights for the residents. Crank up the taxes too high, and you'll get mass exodus as with California today. But with them too low relative to expenses, the states can't provide necessary services (or wind up in significant debt, as we see with PIIGS in the EU; this suggests that balanced-budget rules are necessary for the states, which is a problem we'd need to overcome).

It looks like you're so afraid that a small portion are going to be disadvantaged that you're insisting on a one-size-fits-all solution. But experience shows that such solutions are almost always worse in the end (e.g., NCLB), and by their very nature they hurt a much broader scope of people -- better to make your experimental mistakes at a small scope. Especially since experience also shows that legislative mistakes (again, like NCLB, but there are countless other examples) are almost never rolled back, because of political gamesmanship.

I don't think a strict adherence to the literal wording of the document will be any beneficial to solving the broad problems that exist today.

In what way is insisting on using Article V (the amendment process) in order to patch bugs inferior to ad hoc power grabs? When the changes are ad hoc, we get phenomena like GWB's power grabs around USA PATRIOT and other issues. In some cases these were decried by the other side, but a few years later, when power swung the other way, those that claimed to oppose the overreaches did nothing to right the problems, and indeed, have enjoyed exercising and even expanding those newly-minted powers themselves.

So it looks to me like the ad hoc route has tremendous dangers. The only disadvantage I can see to the use of Article V is that it requires enough political support that those advocating the changes, although they don't admit it, don't believe they can get it (or so it seems to me).

[1] http://openjurist.org/title-18/us-code/section-1111

[2] http://openjurist.org/title-18/us-code/section-1092