The only time we really do taxes currently is when money changes hands, and the only time total estate wealth needs to be calculated right now is at death.
So isn't the easy win to just jack up the inheritance tax? Make it 75% of all wealth greater than 10,000x the median household wealth or something.
The reason that isn't happening when it's way easier to implement systematically and constitutionally, is exactly why this won't happen. Republicans hate wealth taxes and the truly wealthy will just hide their wealth offshore or in tax-sheltered instruments if the taxes get too high.