All that would be needed would be to combine the program with just a spike in enforcement, and that would be enough to get both employers and employees to see that their best bet is to go the legal route. Once it's jumpstarted that way, it will be much easier to maintain it, because the more people go the legal route, the easier it would be to take action against those who don't.
But if you don't agree, all that would be necessary would be to make it clear at the time the program is enacted that this is a pilot program, and that the option of extending it to illegals, if it doesn't work as fast as some would prefer, will be on the table. But holding it up out of fears that it won't be effective enough will only guarantee stagnancy.
I agree. But enforcement has to be focussed on the employers. We already know that we can't enforce the laws by focussing on the illegals. If they cared, they'd be legal.