What about valid notarizations used only for blocks without unwanted votes?

What about valid notarizations where the child block itself is withheld but later released?

What about valid notarizations used only for blocks where NN are the miners?

Depending on internal resource such as coins to determine consensus is very problematic, when it can overwrite others.

This is why decentralization uses external resources for consensus, incentives (from costs), permissionless access, data availability to achieve some type of objective truth derivation that’s more costly to change or alter. Checkpoints and permissioned entry introduce subjectivity and centralize control that can easily alter incentives to favor dishonest behavior.