Interest rates should depend on the market. Why you want to artificially meddle in everything? Solutions for student loans is simple. Stop government guarantees, and get rid of the government law that makes it not dischargeable. Government caused the problem and you ask for another government “solution”

I'm fine with the federal government servicing 100% of student debt and for that debt to be completely interest free.

But that's as far as I'm willing to go on the issue. If it were up to me, I'd have the feds regulate university expenditures the same way that they regulate insurance companies. You get X% of tuition and fees to go towards construction, overhead, and administration. Everything else is for educator salaries.