Not good enough.
Businesses would still be burdened with the reporting and accounting requirements.
And somebody would still be in the business of deciding who qualifies to be tax exempt - which is the issue at hand.
The IRS would still be required.
A large problem is in deciding what is and isn't income. There have been proposals to tax an 'imputed rent' on the house you own. Of course, unlike owning real rental property, you don't get to deduct expenses or depreciation or set your own rental rate.
The IRS can keep everybody busy, all their agents, the CPAs, and the lawyers, just by tweaking the regulations every year on what is and isn't a deductible business or investment expense.
Then you have the problem of mission creep. Suppose we go to the FLAT tax, rather than fire any IRS agents, they'll be retasked to look for small income streams, such as garage sales. Sell your house to your kids, and they'll be auditing what it would have sold for on the open market to make sure you didn't low ball the sale.
The IRS would be somewhat limited in its access to personal information if we went to a sales (FAIR) tax. But they'd also be likely to start watching garage sales and other private party exchanges to make sure the tax was paid, just as would happen with a flat tax.
You really can't cure the government urge to mission creep, but I suppose you can whack that bush down to it's roots every now and then.