I was more thinking fines would be a first strike sort of thing, second strike is either larger fines, or audits, third strike arrests... something along those lines. Fines are the easiest way of saying "we see you, don't do this" and I feel like most people would get the message unless the fine was less than what they save by using illegals (hence make the fines a decent chunk of money), and then go from there for the worse cases.
Always frustrating.