I applaud your effort and am interested in how you're working out the tax implications. $17,000 doesn't come of the top in reality, for the marginal $50k person you'd be taking nearly 1/2 of their take home pay. Seems like a longer repayment would be more fair. Also if you forgive the $30,000 that's still a taxable event for the student; they'd owe the IRS as through you'd given them the money, might cost the student $10,000 or more depending on the person's situation.

Note: 17%, not 17,000. So $8,500 for a person making $50k. But 17% does seem a bit high to me, pre-tax.