Those who are not serious -- which includes a remarkably large number of students, even at good colleges -- would have to back off and go face the realities of the adult world in the job market. But not as many jobs would be able to require college degrees if such degrees were no longer so readily available at someone else's expense.
If individuals issuing stock in themselves sounds impossible, it has already been done. Boxers from poor families get trained and promoted at their managers' expense, in exchange for a share of their future earnings.
Even some college students have already gotten money to pay for college in exchange for a share of their future earnings. However, in the current atmosphere, where college is seen as a "right," there has been resentment at having to pay back more than was lent when the recipient's degree brings in large paychecks.
What is truly repugnant to some people about college students issuing stocks as well as bonds is that this not only takes the government out of the picture, it takes the intelligentsia out of the picture as prescribers of how other people ought to behave.
Reality can be hard to adjust to. The most we can do is see that the adjustments are made by those who get the benefits, instead of making the taxpayer the one who has to do all the adjusting.