Pres. Bush would probably consider his current course of across the board marginal rate lowering a "major" overhaul of the system. I, on the other hand, while considering this welcome change, certainly would not label it "major" overhaul.
In the President's defense on this matter, that may be all he can muster. The progressive income tax is the cornerstone of the modern liberal redistributionist schemes and the ATM card for the governmental nanny state of both the left and right. He can expect the fight over any major change of this system to be brutal, perhaps even more so than the battle over Social Security reform. Tearing down the golden symbol of American socialism is one thing, but dismantling the "progressive" tax system that makes it and countless other nanny state programs possible, is an entirely different animal.
Pres. Bush can expect the class warfare to reach levels of ferocity beyond anything US troops have yet encountered in Afghanistan or Iraq. American socialism has grown and thrived since the 1930s. It is so entrenched in the American mindset, that its attempted removal will inspire leftist hatred that makes that of the last four years look like a Sixties "love-in." If you think Pres. Reagan was reviled for his tax cuts, just wait until there is an attempt to scrap the current system.
This, of course, brings me to my definition of "major." The tax system as it now stands is so distorted and corrupt that it would feel more at home in the UN under the guidance of Kofi than in the land of the free and home of the brave. It has far passed the time for us to level the current tax system much as if it were a Hamas hideout standing before a row of Israeli dozers. It is time to lay waste to the 16th Amendment and bring down that behemoth that is the IRS. The system as it stands is a cancer beyond treatment. Not even aggressive chemo will work; it is time to amputate.
With that monstrosity out of the way, we could implement something bold and exciting. Many would like to see something along the lines of Dick Armey's Flat Tax. For me, this doesn't go far enough because the IRS and the 16th Amendment would remain in tact and system would be under immediate assault by those wishing to twist and distort it into something resembling what we now have.
Personally, I would like to see something closer to the Fair Tax which is basically a national consumption tax. Yes, this idea has some problems, but they are problems that could be worked out much easier than the problems of our current system could be fixed. The larger point here is opportunity.
America was founded as a land of opportunity and it is past time for us to take advantage of that opportunity and scrap the current system for something better suited to how we now live.
UPDATE: There's an interesting discussion of taxation over at An Inclination to Criticize.
UPDATE 2: I posted this over at Blogcritics.org