While I agree with you in principle, I would never take that bet as a lender. What incentive would there be for a 22 year-old graduating college with a heap of debt and no assets to not declare bankruptcy? In 7 years - when they're 29 - they'll have a clean credit record and the earnings and investment on $student_loans worth of money. Planned well, you could easily be in a position to have a huge down payment for a house saved up the minute your bankruptcy falls off the credit report.
You can't (and shouldn't be able to!) repossess human capital. Knowing this, the smart kids would be baking in a high-cost education and bankruptcy as a part of their plan. I think the only way something like that works is if you have someone with assets co-signing the loans - ie, the parents - and that still raises barriers for smart kids whose parents don't have significant assets.