So long as you are going to pass a constitutional amendment it might as well be to outlaw income taxes all together then the problem you describe solves itself.

So long as you are going to pass a constitutional amendment it might as well be to outlaw income taxes all together then the problem you describe solves itself. Even if the tax code were as simple a "straight 10% no matter what no exceptions" there would still be a market for tax software because a large number of people can't do basic math.