This is already the model for a few STEM majors in graduate school. My tuition and a stipend were covered when I was in graduate school, while those getting PhDs in English or Sociology had to pay their own way. This has been the case for decades.
Personally, I think that universities should be required to make full disclosure to prospective students on the employment prospects of their selected major. When the "Occupy Wall Street" protests took place, it seemed that many of the protestors were complaining that they had college degrees but could not get hired anywhere. However, few of them complained that their college degree was in a useless subject, and it is likely that most of them still have not figured that out. Instead of blaming Wall Street for not hiring them, they should have turned that anger and frustration against the colleges and universities that charged them thousands of dollars on worthless degrees.
A STEM degree takes real work and many students just are lazy.
Re: “My tuition and a stipend were covered when I was in graduate school, while those getting PhDs in English or Sociology had to pay their own way. This has been the case for decades.”
Another little known fact....
Foreign PhD STEM students almost always get the same tuition and stipend that Americans get!