Could the income tax be turned into a a progressive consumption tax for all but some of the top 1%? I think it could, by allowing Americans to contribute up to $5 million lifetime before taxes to an IRA. Withdrawals would be allowed at any age and would be taxed as income. You would also want to raise the rates a bit and eliminate the corporate tax, the corporate tax being a tax on saving and investing.
This would greatly simplify my tax return!