Under your proposed system, no politicians of sufficient office would ever be tried for a crime related to their office (as long as it was for the right reason)

Under your proposed system, no politicians of sufficient office would ever be tried for a crime related to their office (as long as it was for the right reason)? This seems like a very poor incentive system. I do agree with you that prosecution would not be good for stability. However, maintaining a separate rule of law for those in office is not good for stability, either.