The "billionaire flight" problem actually illustrates perfectly why you need a wealth tax in the first place: to prevent billionaires from having undue levels of power and consequence on the populus. When you let individuals accumulate outright unreasonable amounts of money you give them a single random individual, with no governing credentials, whose choices should have no bearing on others the ability to indirectly effect the economic fate of thousands or millions of other people just because of their selfishness (to the extent that effects actually materialize, which to large extent they don't anyway...) It's outright laughable that any government would consider giving individuals such power over the fates of the people they are supposed to serve, represent, protect (at least in the liberal democratic tradition).

Humanity should not strive for kingship, whether minted through "god given right" or coin. We should strive for collective, distributive, balanced control of resources.