Hence the:

>There should be nothing that the executive branch does in terms of investigation and prosecution, that the average citizen should be legally barred from doing.

>This includes prosecuting crimes in criminal court, requesting and enforcing warrants, and so on.

>The only difference between an average citizen and the government employees doing these things should be that the government employes are being paid to do these things as a full time job.

If the cops botch their investigations... Well there's nothing stopping anyone else from conducting their own. Might as well conduct one into the cops botching of the investigation too.

What makes you think someone prosecuting a police officer would rely on the police investigating the officer?

they already have an incentive to botch investigations when their buddies are involved. Maybe this makes the incentive slightly greater but you shouldn’t rely on cops to investigate their buddies anyway