Big Sur’s sealed System volume seemed like a good idea. Although the read-only version in Catalina may look impregnable, guaranteeing integrity using a Merkle Tree of hashes, then locking the whole lot in a snapshot, looks even more robust. Like other good engineering ideas, though, it also needs thinking through thoroughly.
It’s locked down for your own safety, though. Giving up freedom in exchange for safety never hurt anytone, right?