Actually, we had such a thing in Florida. In lieu of a state income tax, there was this creation called an intangibles tax that was levied on all personal financial assets. Each year, you toted up the value of your cash, savings and checking accounts, stocks, mutual funds, bonds, and any other monetary instrument (retirement savings were exempted) and paid a small percentage (around 1%-2%)of that amount. The system was scrapped several years back due to enforcement difficulties.
I think imposing a similar assessment on rich DemocRATS is a fine idea, but at a much higher percentage (say 25% annually). Dillweeds like Buffett and Gates don’t have much in the way of real income, so they can piously (and hypocritically) talk about raising income taxes on everyone else. I suspect they’d start singing a different tune once their wealth and assets were targetted and they actually had some skin in the game.
Perhaps a smart plan would be for government to require a pre-payment of the value of the foregone capgains and estate taxes to be remitted prior to establishing the tax exempt foundation. At least we'd be able to make honest men of those vocal tax advocates.