Here's my prediction: The Fair Tax will never become law. The two most powerful congressional committees are the House Ways and Means and the Senate Finance committees. These committees write tax law, and as such they are able to confer tax privileges on some Americans at the expense of other Americans. The Fair Tax would reduce or eliminate this form of congressional privilege-granting power and, subsequently, campaign contributions from the beneficiaries would dwindle.
The method used to finance the federal government is very important, but I've always argued that government spending is the true measure of its impact on our lives. If there were a Fair Tax, what's to stop Congress from deficit spending or inflating the currency? Deficit spending and inflation are simply alternative forms, albeit less obvious, of taxation.
You say, "What's Williams' solution?" My solution is an amendment limiting federal spending to a fixed percentage, say, 10 percent of the gross domestic product. You say, "Why 10 percent?" If 10 percent is good enough for the Baptist Church, it certainly ought to be good enough for Congress.