The income tax really doesn't hurt the top guys. They have their tax havens overseas.
A VAT would be useful, because you can't hide a Maybach like you can some bonds in an offshore account. However, sales taxes are regressive in general, and again, the burden of it would be on the shoulders of people buying basic stuff to survive.
A tax system is a debate into itself. You need a number of factors in it:
1: Some progressive-ness. People just getting by need a bit of help, so it can't just be taxing food, housing and other staples for survival. A percentage point or two on a luxury car might be better than taxing WIC goods.
2: Enforcability. You get to a certain wealth level in the US, you pay $0 in taxes. You don't want a "soak the rich" mentality, but there is always having people pay their fair share. If income taxes could be enforced, it would bring a better share of revenue.
3: Encouragement/discouragement. In some circumstances, it might be better to tax some good heavily rather than outright ban it. On the other hand, it might be better to have no taxes on certain goods in order to get people to go buy it. LED bulbs come to mind as something to encourage people to buy.
The Fair Tax sounds interesting, but it puts the tax burden on the people who can least afford it.