Making rules that avoid triggering irrational behavior is rather hopeless by definition though. For all we know a regulator once dated someone who worked at a company and the bad breakup makes them spiteful against the whole organization.

The solution there has to be oversight to identify when a regulator is misbehaving.

Though I'm fine with limiting their ownership to zero for purely rational reasons. A few thousand bucks worth of loss/gain might still sway small borderline decisions.