So a VC gets your income, instead of the bank from which you got your loan, under the current system? Doesn't sound like it would be much different from how it works today, in practice.
The key is that in an 'equity' based program, the most successful graduates pay for the mediocre ones by having a higher salary to pay dividends on, whereas in a debt based system the integrity of the system is ensured by squeezing every last drop out of the least successful graduates.