This is maybe one of the purest examples of the Bell Curve Meme in software engineering. The things you would do to the system Tailscale operates to eliminate all single points of failure (generally, and in the specific case where, where the "single point of failure" applies only to a small cohort of customers) would make the system less resilient, and increase failures.

Generally, you do complex distributed systems without on-paper single-points-of-failure anywhere when you absolutely have to, because those systems don't have transient failures. That's not mesh networks like Tailscale at all.

As always: https://how.complexsystems.fail/