I know this is likely impossible.. but I'd love to see prosecutors/law enforcement have to serve out the sentence or someone they convicted via misconduct. Withhold or manufacture evidence to push for a 10 year sentence? Sure but if that's ever uncovered, you get the 10 year sentence instead.
It might convince everyone to be a) more forthcoming with evidence and b) reasonable in the penalties they seek. Both could be a win for the system and the public as a whole.