Well you are wrong about that in regards to Rebates. As long as rebates are uniform they represent a tax reimbursement which is completely constitutional.
The goal for the FairTax with regards to the Rebate is simple:
THERE IS NO FEDERAL INDIRECT TAX APPLIED TO INDIVIDUALS BELOW A CERTAIN SPENDING THRESHOLD OF ESSENTIALS.
To implement the above the government can choose business to choose to monitor spending of all consumers, a ridiculous and impractical proposition. Or the government can rebate/reimburse taxes already paid up to that threshold.
The income tax has always been constitutional as an indirect tax under the historical provisions of the Constitution as long as it was uniformly applied in the same manner as an excise tax. It is the graduated income tax which is not uniform for which the 16th was created. The 16th allows for confiscation of wealth and for targeting which wealth groups get taxed.
The original income tax was signed into law in 1862 by President Lincoln and was 1% on all incomes. It was constitutional and never challenged. It was Congress that in only two years time after Lincoln signed the original law that they started to create tax brackets that led to a graduated income tax. This graduated income tax was challenged in court and was declared unconstitutional by the SCOTUS later in the 1860s. The 1% tax was recuscitated in the 1870s and sunsetted in one year’s time but there were again members of Congress wanting to make it graduated despite the SCOTUS precedent. The income tax was again brought up in 1894 and shot down. This was the history leading up to the 16th.
So as long as the income tax was applied to incomes uniformly this form of taxation was considered constitutional. Ever today some IRS supporters use twisted logic to say the income tax is uniform by saying that within each bracket it is uniform. You can bet that they will try to use that argument should the 16th be repealed.
Really, what you need is a CONSTITUTIONAL AMENDMENT that rescinds the 16th and creates something new.
Remember, any percentage levy (an income tax is such) is the dead hand of the past reaching out to throttle the future.