That’s for others to work out. But, for example, the government could declare a “grace period” of a reasonable time, let’s say a year, during which illegal aliens could go back to their home countries and get a visa from a U.S. Consulate like legal aliens do. Most of them go back home from time to time anyway, for other reasons. Let’s say there is a “Level One” (fairly superficial) vetting at that time. If the alien passes it, he gets a visa and, if he was working before, a work permit to continue doing the same thing. During the ensuing year (year two) they would undergo a more in-depth “Level Two” vetting. Anyone with questionable results could undergo a “Level Three”, very intensive investigation which could result in revocation of the visa and deportation.
Anyone with a serious criminal record, suspected terrorist ties or who is found to have misrepresented anything would either not be approved to begin with or have the visa withdrawn.
Keep in mind that legal aliens have to do all of that, but in a much slower process. I do not see what’s unfair about something of that nature
Now for the radical part. After that first group, immigration numbers would then be determined by an independent body; something like the Federal Reserve or even a branch of it, that would base immigration on the nation’s demonstrable need.
So, for example, during the earlier Bush years, when unemployment was actually negative, it could be increased, in times like now it could be decreased.
A citizenship path, of course, would be another thing.