Then you might like this idea: index income and wealth tax rates to the Gini coefficient measure of inequality:

https://medium.com/the-national-discussion/how-to-stop-the-plutocracy-game-index-the-top-1-s-tax-rates-to-decreasing-inequality-a3a19f42cd97

If Gini drops, the rich get a tax cut. If Gini rises, their tax rates rise.