I really like what you’ve written, with one exception. An oligarchy inherently means a system of government (official or unofficial) run by the wealthy. What you describe doesn’t have a feedback loop through control of law or regulation. I think it’s implied, but one could imagine a system where there are obscenely wealthy people aggregating money at marginal utility approaching zero, where those same people have no actual power in the government.
Heck, the British monarchy is a real-world example - near zero influence on government and extreme wealth.
