>Fix the loophole where billionaires use their unrealized assets as collateral for borrowing. When they do, make those as realized assets and tax them. Don't apply a blanket unrealized 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.