"That way other workers could report their employer for hiring cheap illegals."
No luck there. First of all, the actual people involved have protection from liability as a business so the business gets fined and nobody goes to jail. Second, in the US the accused has the right to face the accuser. WHO reported the company will be in the paperwork and will also be a matter of public record.
By the way it is already a crime to hire illegals, and to pay them less than american workers, and it is already a criminal affair. The system doesn't work particularly well.
You can anonymously report a crime, but you can not anonymously accuse someone of a crime. No employee is going to lose their job by reporting their employer for anything.