Wealth is not income though. Higher wealth taxes would go a long way but then you again have the problem of the wealthy simply moving their wealth out or not bringing it to the high-tax country in the first place.
I could easily see any nation trying to implement higher taxes on the rich to also implement a wealth export tax that takes a tremendous portion of their accumulated wealth if they try to jump ship and take it overseas.
> not bringing it to the high-tax country in the first place.
This is the larger concern, but if a society can't survive without the good graces of the lucky rich, it is already their slaves.
Or they can penalize countries who operate tax havens - it's not like tax havens represents a significant amount of either trade or GDP.