We would end up with massive conglomerates who owned 500+ companies of 4999 people, and if that didn't work you'd just get simple collusion where everyone knows

We would end up with massive conglomerates who owned 500+ companies of 4999 people, and if that didn't work you'd just get simple collusion where everyone knows company A and B are owned by the same person so they try to cooperate even without being explicitly ordered to.