"Asymmetrical warfare" is a strategic and operational concept, not a threshold on some notional tech tree. It's a mental tool that people reared in the paradigm of high-tech, high-intensity combined-arms mobile warfare - in other words, Americans - can try to use to think about warfare as pursued by people who don't have the logistical support or unassailable strategic reserve that makes it possible for us to win wars the way we do.

This would certainly be the case for a billionaire, who simply cannot swing the resources to sustain the logistics to support the kind of formalistic, resource-intensive combat you envision. In a realistic scenario the strategic and economic balance is going to look like the American Civil War only much more so, inasmuch as where the Confederacy at least at the outset of the conflict had an economy it could dedicate to supporting the war, a billionaire, as I've already touched on nearby, not only lacks such power but indeed requires unfettered economic access to continue to exist, a vulnerability he constitutionally cannot answer since it inheres in the source of his power...again just like the Confederacy, which relied on trade in raw agricultural outputs to supply itself with the tools and materials of industrial warfare, and so saw its back broken after the Union suppressed that trade by blockading southern ports.

But at least the Confederacy had an economy, however incompetent. What, I ask again, does a billionaire have that an army can't take away?