The point is how do we stop people coming illegally? Just because we issue say 5 million temp worker permits a year doesn't mean the other 6 million people who want in are going to say, "oh well US is full up maybe next year". No, they are going to come across the border on their own. Which puts us right back where we are now.
Well, for seasonal farm workers and or unskilled workers, I think the foreign workers would be required to register for work when they apply to come across the border. And their employment would be brokered by licensed labor contractor services. The employers that need foreign labor would go through the labor contractors. The contractors would be responsible for transporting the workers to and from the border stations and to and from the job sites and also for assisting the foreign workers with temporary housing and other needs. The employers would not pay the foreign workers directly, they would be billed for labor services by the contractors who in turn would pay the workers. The employer would not need to collect any information whatsoever from the foreign worker and it would keep his labor management/compliance costs and risks down.
And this would be a much safer, more economical, more reliable and more convenient system for the foreign workers. I think there would be plenty of incentives for the workers to take advantage of the system rather than risk illegal border crossings, roundup and deportation. I also believe that the legal workers would spot illegals very easily and would assist in getting them into the program if practical or out of the country.