The potential solutions are three fold:
1. Limit growth of students - impossible if your organization received venture capital.
2. Reduce the cost to educate - Unfortunately if you make education a commodity, ironically it will be replicated, leading to alternatives, ultimately leading to (1).
3. Guarantee the loans somehow
I think the only type of organization that could pull it off is one that doesn't mind waiting a long time to do it sustainably. Probably a not-for-profit. Alternatively, you could sustain it by doing it at a loss, e.g. you have some other organization to ensure (3).
This all works unless the instruments aren't audited well where the risk is higher. (think: ratings agencies in the housing crisis) Here the risk is that payback is bad, but we don't know yet, so investors are left holding the bag.
This latter scenario is really only bad for the investors and wastes the student's time, but then again the current college system already does this, so at least this doesn't shackle them with debts they can't pay.
Of course later investors won't buy the ISA packs if they first blow up, but seemingly no one gets hurt if it all goes up in flames.