I can't see how the operation you describe here is defined or possible for any blockchain that hosts more than one smart contract. Just for a start, how do you decide whether to include a smart contract upgrade that the majority of verifiers doesn't care about either way (surely the most common case)? It's like saying that legislation doesn't matter because we have elections. The elections (consensus) produce the legislation (allowed transactions). You can squish those two layers together, but starts to break the premises of the underlying system (e.g. DAO fork).

I would love to know what software system you were thinking of when you wrote this. Or were you? Sincere question.