Even today, millions of taxpayers pay quarterly extimated tax payments ... no withholding. It's not that far a stretch to expand that population. Every April 15, millions more taxpayers write checks to cover their outstanding tax bill ... funds not withheld.
From an implementation standpoint moving to eliminate withholding is trivial compared to implementing the FairTax. And from a philosophical standpoint, I'd guess there would FAR greater agreement among taxpayers to lobby for withholding elimination, or to at least make withholing truly voluntary, that there currently is to lobby for the FairTax.
Trying to destroy something is far easier that trying to create it in the first place. Why don't you try it?
You are correct that many already pay estimated taxes without withholding but that doesn't cover the tens of millions of workers who don't nor does it touch the underground economy. The IRS police would be out in force finding and threatening those who don't comply and those who change addresses often. Threat and intimidation are the primary instruments of the government and that would by nature increase. The number of enforcers would increase dramatically by necessity and we would have more government union members whose money goes to the Democrats. I think eliminating withholding will be impossible.
There are many more reasons for changing the method of collecting taxes than revealing the amount of taxes paid. There are still many hidden taxes embedded in the system other than the income tax.
I am amazed at the furor shown by some, not you necessarily, about changing to the fair tax. At worst, granting all the misinformation and lies spread here to be true, it is still far better than the present system or any other so far proposed.
Why don't you get behind it? Be forewarned that my standard reply will be it is still far superior to what we have.