Your scheme only captures the biggest idiots. There are plenty of ways that require much more sophisticated methods to detect. An example is insider reciprocity

Your scheme only captures the biggest idiots. There are plenty of ways that require much more sophisticated methods to detect. An example is insider reciprocity: an insider at company A trades inside information with an insider at company B. They both profit from the insider information but neither trades in the instrument for which they could easily be flagged as an insider.