Easy problem to solve.
A wealthy native citizen who escapes taxation by becoming a citizen of another country, should have most of his wealth confiscated by the native country he is leaving as an exit fee.
Why should the taxpayer -- who earned his wealth -- be held responsible and penalized for his government's greed?
This isn't a financial issue; it's a moral issue. A question of individual freedom vs statist greed.
lol
you assume the rich aren’t smart enough to move their money out gradually over time undetected.