I just don't see putting in a National Sales Tax as having anything to do with cutting taxes.
Your taxes will be cut because they would be shifted from your income to consumption. You choose how much you spend, therefore you also choose how much you will be taxed! You will also get a rebate on taxes of necessities up to the poverty level.
My worst fear is that we'd end up with a National Sales Tax AND a National Income Tax.
The purpose of the Fair Tax is to eliminate income tax. People who support the Fair Tax will never condone an income tax and an NRST.
One fact remains even if you ignore all the above facts. The IRS and its 60,000+ page tax code will cease to exist! The only way to eliminate your fear is by getting involved to make sure your scenario never happens.
The deal could always be changed later once this system is set up. There's nothing to prevent that from being done.