Or just rank em by salary/comp. More skilled people => more valuable to the economy => receive higher salary => more likely to get visa (=> pay more in taxes).
The end result is the same: the most valuable workers are let in. It'd also have a small, but nice benefit: a voluntary revenue stream for the US to spend on whatever it would like (perhaps improved education and training for citizens).
Never really got around finishing it and pushing it out tough, although I am curious to see what the feedback is on it.