So make income tax a deduction on a wealth tax, and avoid penalizing people who do indeed pay top marginal rate income tax on a large salary/bonus. Given that the ultrarich pay very little to no income tax then Paul’s argument is “don’t increase my income tax from unnoticeable to 20%”
$tax_paid = max($income_tax_liability + $capital_gain_tax_liability, $wealth_tax_liability)
...that does seem like it would seem to alleviate PG's concerns about adding "a mere 20%" to the income tax rate.