Some thought on this particular idea....
I think that loan maximums need to bear some kind of quantifiable relationship to the expected income of the degree being pursued. Clearly, unlike a mortgage or a car loan, any method of estimating this will be very imperfect. Incomes are going to vary geographically, for instance. Many people won't stay in the workforce long as life situations change. And on and on. The variables are many.
But it seems like something coupling these two values is preferable to nothing.
That being said, it's (probably?) the case that a degree from Notre Dame is worth more, on average, than a comparable degree from IUB or Purdue. Or compare Harvard or MIT to UMass Amherst. But it would also likely be true that a degree from ND would be worth more than a comparable degree from Valpo or Hanover.
And, of course, there would also be variance in expected income between, say, a Bachelors in Elementary Ed from Purdue and one in Chemical Engineering.
It's never made any sense to me, in a strictly financial sense, that all degrees at a university carry the same tuition.