i think Canada should look at taking in perhaps 30,000 "Dreamers" as a pilot project, but only after testing and review of the credentials of the applicants. Perhaps exams or IQ tests would be another thing Canada could do to determine the top Dreamers to allow in. 
It would be in Canada's best interest to skim off the Best of the Best Dreamers. Canada needs smart hard working people. They would probably be a big asset to Canada and able to blend into Canadian society immediately.