The warrant here was approved by a magistrate judge, and I would suggest making the process for approval more robust to reduce this kind of abuse.
Personal civil liability and firing can also help.
Personal civil liability and firing can also help.
I do agree with you in general that we should aim to split system functions between multiple people. But this merely raises the bar, it doesn't make corrupt actions impossible. Which means we should be focusing on both avenues of reform, rather than emphasizing one to downplay another. Especially as when you do this, the entrenched system seems to takes advantage of the downplaying while resisting the solution being emphasized.
You could make the system more adversarial at that point, although I think enforcing bail hearings where a public defender can argue would help in this and many other cases.
But even then, abuse of that classification is something that could routinely happen and would need to be punished post-facto. Imagine the same sheriff looking to perform the same retaliation, so he checks all the boxes for a no-notice no-knock warrant that still results in an arrest with a weekend in jail. Which is why my main point is that we shouldn't argue against one avenue of reform with the goal of emphasizing a different one.
And once again there isn't much that can be done about corrupt public officials unjustly prosecuting/persecuting former officials as it comes down to that same human problem rather than a system problem - regardless of whether there is or isn't criminal liability for actions adjacent to official acts, they are still subject to the rest of the law! For example James was persecuted under the guise of having defrauded an unrelated agency in a personal capacity, independent of her actions as an official being what drew the aggro. Those persecutions of Comey and James basically rely on a post-truth electorate that doesn't care, and who chose to reelect a destructive tyrant who repudiates our American values merely to stick a fork in the eye of "the elites".
And while we can also talk about ways of reforming the system to prevent that (eg Constitutional amendment that explicitly divides power amongst independent agencies), I don't think it has much bearing on how we should be drawing legal lines in the sand to constrain public officials.