Our entire education system is jacked up 10 ways from Sunday, and the funding of it is just a small piece of that pie.
I totally agree of tying loans and interest rates to the probability of a degree landing an income-producing job. The more "needed" the job, the better rate.
To be honest, I don't care if someone wants to get a degree in gender studies or sociology or whatever, I think a significant reason for college education is learning for learning's sake. Just don't make me pay for it when you can't get a job.
In the bigger picture, we need to look at the way college is structured and ask if it's efficient. The short answer is, no. The bigger answer is it's bloated to be income producing for the University, most of which goes to administration. The rate of inflation for college education since the early '90s has gone nuts.
I also advocate programs in which the tuition is covered if you contract to work in that field for 'n' for years after school. We see that obviously with ROTC, also with some of the trades, nursing, etc.