Honestly, I think for many countries it might require very far reaching constitutional changes to actually tax the ultra wealthy.
For the USA, an amendment was needed to introduce the income tax.
Another amendment might be needed to introduce a wealth tax.
And a legal distinction would need to be made between the property of the common man vs. the ultra wealthy.
That 14th house, yacht and the hundreds of billions of the billionaire currently enjoy the same legal protections as the owner-occupied single family home and that family’s meagre savings account and the car they need to get to work.