The single most crucial preventative measure that must be put into place, and it must somehow be made immune to corruption, is a battery of psychopathy tests for anyone seeking office, or any position of authority. Psychopaths must be identified, filtered, and where possible, sequestered for specialized duties where psychopathy, like autism, can be harnessed – just not in the public sector, where their sickness stands to endanger the people.
Also, "Senator" and "Congressman" must be eliminated as career choices. The lobbying industry must be ripped by the fucking root from the rotten soil that it grows from. One thing Ghaddafi got right was to make sitting on legislative councils a mandatory civic duty, like jury service. The Green Book was demonized for understandable reasons.