This makes the most sense. The trick is to tax all realized value.

I’m happy for billionaires have their net worth go up, as long as it can be taxed if any amount they realize.

So this includes using their networth as collateral, donations (even to charities) and passing as inheritance (which should be taxed upon death)

And if the margin all tax rate over a 1 million is extremely high, then it’s pointless being a paper billionaire. People would actually spend their wealth and contribute to the economy