There is a passage at the end of a recent Economist article about the debt problems faced by developing economies that suggests a more flexible form of financing is possible not only for countries, but regions, industries and even individual businesses (including the self-employed individual):
"...the IMF finds that most of the recent increase in emerging-market government debt has been due not to bigger primary budget deficits, but to large swings in exchange rates and interest rates. Emerging economies need to reduce their reliance on foreign-currency and short-term debt to make interest payments less volatile. Another interesting idea suggested by the IMF economists is that governments could issue bonds on which the interest payments would be linked to a country's growth rate: the faster the rate of growth, the higher would be the interest rate paid in any year. If growth slowed, interest payments would fall, providing a useful cushion in times of economic stress. It is an idea well worth further consideration."
The International Monetary Fund report referenced is available as a PDF here, for free. The notion of a variable interest system based on growth rates could be applied across a wide variety of economic situations. Consider, for example, financing of college educations, in which the economic value of a chosen major were later applied to the interest rates of student loans -- if a student chose a very risky major and the jobs vanished due to obsolescence, loans could be forgiven completely to facilitate a return to college to study a different area. Business that strived to clean up polluted sites could be financed based on the risk and reward to society, with lower rates if the work was not as profitable (or at all profitable). Society, since it provides the capital used in banking, can set these kinds of priorities and, as a result, emergent polities, groups who invest together and in one another to accomplish some social goal, can become a viable economic entity in an environment in which the cost of money is variable based on other factors than simple bottom-line economics.
Two good books on this subject are: