Given that you yourself mention the figure of $100 million, did you perhaps misunderstand the proposal and think that it applied to unrealized gains on any asset theoretically worth more than $100 million? The criteria proposed were not such that merely having share options in a private company with some theoretical $100 million valuation would classify you as having $100 million in wealth for the purposes of the tax.

This would require taxing people on the market value of their home pre-mortgage deduction(which is the exact same scheme as what billionaires use just on the smaller scale),which would never pass anywhere.

I am not a lawyer, but I suspect waiving the deductibility of interest expense/debt based on wealth would be blatantly unconstitutional in virtually all of EU.

That's what property taxes are. Most people's largest asset is their house. So actually most people are already paying taxes on unrealized gains. It's only genuinely wealthy people, who generally have more valuable assets, that don't.

> Now you're paying a cash tax on $100m when you can't even sell anything.

It's impossible to write the law to avoid this type of situation?

> When [billionaires use their unrealized assets as collateral for borrowing] make those as realized assets and tax them

That works too! And also ban buybacks. If companies want to return profits, pay dividends.