And no, if you want to make a consumption tax regressive, you don't have to make it complicated. You can exempt the first $X of purchases, where $X is some "living wage" line according to some politician's favored theory. You now have a progressive tax.
That's not progressive; that's regressive with a discontinuity. For example, assume the sales tax rate were 25%. In that case, a middle-class person making and spending 2*$X pays 12.5% (25% * 50%), which is a higher tax rate than a rich person who makes 10*$X and spends 5*$X, who pays 10% (25% * 40%). And the really rich person making 100*$X but who ran out of things he wanted to buy at 10*$X has a tax rate that's even lower than that: 2.25% (25% * 9%).
By the way, I wrote that example using easy numbers to illustrate my point. The actual difference in saving rates between normal people, the rich, and the very rich is large, but not quite that large (see the second chart on this page). However, even at realistic savings rates (2.5% for the bottom 90%, 15% for the top 10 to 1%, and 35% for the top 1%) the principle is still valid.
And since everybody would be helping to carry the load of the government they ask for, the big winners in this system are the upper middle class, who are currently getting screwed from both ends of the income spectrum.
On the contrary! As you can see from my example above, the middle class person making significantly more than $X, but not enough to easily save a large fraction of his income, pays the highest tax rate of all. The peak tax rate would occur somewhere around the 50th income percentile, while if the goal were to be progressive it should occur at the 99th percentile.