I realise that the US has a progressive personal income tax scale, but my impression (as a foreigner) is that it's severely gamed at the upper end. Didn't Warren Buffet once point out that he pays less tax than his secretary, despite being a billionaire (and presumably with the income to match)?

If this is the true (that high income earners pay very little personal income tax), what you're suggesting would remove all tax on foreign capital and shift nearly the entire Federal tax burden on to middle and low income earners. And I thought the Republican proposal was to halve corporate tax rates and make up the revenue by taxing domestic consumption (in the form of a CFT).