As somebody who comes from a country(India) that routinely loses smart people to the US, your suggestion is welcome.
But, think of this from your perspective. You can try almost as hard as your want but there is no way you can build a system from which you can harvest disproportionate amount of smart people from a population mass continuously. The only way to get them is through immigration.
Take your net population, Subtract the elderly, children and other dependents(people with medical conditions etc). Given poverty, lack of opportunity, overall direction in life, nature of human capital and personal enterprise. Only a very small fraction of people in any country eventually go on to do things of huge value for everybody else.
The only way to get such people in bulk quantities is from outside your country.
Forgive me for saying it. This immigration debate will go on forever, and people will keep talking of citizens vs outsiders debate, every time they miss out on a opportunity. But everyone deep down knows if the US has to keep its economic and military might, the only real way is to get those smart people, have them do something amazing of huge value and use that to keep your way of life going.