Student loans - time for change in repayment options?

Jenkins MBA students at NC State will soon be getting their tuition bills for spring.  Many will be borrowing money to cover the bills.  How should repayment terms be established?  Today students are asked to pay off the entire borrowed amount over a 10 year time period, similar to a car loan or a mortgage.

For most students, investing in college and graduate school has an ROI of 10% or more.  But there is risk involved especially because the earnings streams of gradates vary tremendously both within the same field of study (some engineering grads earn more than other engineering grads) as well as across all fields of study (engineering grads earn more than liberal arts grads).

In a recent WSJ column David Wessel considers whether the repayment schedule should be set in terms of percentage of income.  Currently this is an option for borrowers, but very few select it.  Two Michigan economists propose that all borrowers be put into a system where repayment is based on income, with those having higher incomes having higher payments than those with lower incomes.  This has desirable risk sharing aspects as it automatically reduces debt repayment obligations if one's income falls.

However, it effectively acts like a tax that reduces the incentive to move into a higher bracket.  By itself the effect may be modest, but when combined with eligibility for other government benefits, the disincentives could be sizable.