google and wikipedia tell us that Soft Loans have already been defined as:
"a loan with a below-market rate of interest. This is also known as soft financing. Sometimes soft loans provide other concessions to borrowers, such as long repayment periods or interest holidays. Soft loans are usually provided by governments to projects they think are worthwhile. The World Bank and other development institutions provide soft loans to developing countries."Enforced Ability-based Soft Loans are loans without fixed date or amount repayment terms, based on the ability to repay, but mandatory repayment when the ability is present. I could argue hijacking the word "natural loans", on the basis of the natural mathematical efficiency of enforced ability-based soft loans, but it would confuse.