What if they issue a legal status to all but those who are criminals and let them all stay in forever and make sure that henceforth nobody new tries to enter and become illegal any more. may be this way it will cost less and also the labor shortage problem gets solved. Also give conditional legal status like no social security benefits and limited Medicare only for emergency purpose so they all need to work and earn money and contribute in GDP and taxes and do not rely on govt or other private funds.