Just increase the tax on dividends and capital gains in a progressive manner. And be prepared if the economy slows as a result (not up to date on what economists report there). Spain has a wealth tax and their economy is not doing so well. Everyone in Spain shields it by putting it in real estate and putting a business around it. And nobody can sell their business as that opens them to the wealth tax, so you get wage stagnation, and a general economic malaise as zombie companies limp along.
Nice flashy website though.