They way you ensure they must pay a competitive wage is by retaining free labor markets.
If immigrants are free to decide what to study, where to work, who to work for, what jobs they wish to pursue, and so forth, then SV will have to pay enough to convince them to become software developers in the valley, rather than lawyers, real estate agents, drywall installers, dental hygienists, registered nurses, physicians, and so forth.
It turns out we have an immigration system that does this. it's called, wait for it... immigration, and the US takes 1.2 million people into the country annually under just those conditions.
It turns out that immigrants who are free to pursue their own path in life aren't interested in working in loud, open offices and staring at computer screens for hours a day working on JIRA tickets for the salary that SV feels it should pay.
As a result, SV employers have lobbied for a system that allows them to control who is allowed to come into the country, and the conditions under which they are allowed to remain here. They certainly are not lobbying for any system that would preserve freedom for immigrants.
There's a desperate need for immigration reform, as right now, it's mainly based on family reunification, which leaves a lot of people out in the cold.
But really, seriously, don't look to SV, or Zuckerberg, or Brin, for meaningful solutions. They have an agenda, and this agenda runs through their very secretive HR departments.