> to create a rule that all (...) require unanimous consent?

What you describe is pretty much what has happened and still is happening in Hungary.

The conclusion here is that even if the majority agrees that these rules are against the spirit of the democracy, there's nothing practical to do against them. So yeah, checks and balances are important to have in practice, not just in spirit.

When you're relying on self-imposed limitations, radicals will sooner or later take over and do whatever necessary to stay in power.