Here's a thought: set the de minimis exemption equal to whatever the largest individual tax burden thus far was & keep moving it up each year if necessary. That way almost everyone should at least be able to pay their taxes without being taxed even more.
Discussion
This is sausage making a bit, but the previous levels were meant to be the same as the foreign currency exemption. It’s obviously not the same thing, and deserves a *very high* threshold, if at all