Interest rate and documentation.
Pretend that a batch of YC startups are all getting loans rather than ownership purchases. What effective interest rate are they paying? What is the default rate where the startup dies before acquisition/profitability/IPO?
Write a heuristic to determine a fair interest rate given the current prevailing rates, financial history of the company in question, financial history of similar companies, and similar objective and quantifiable subjective factors. Document it. When someone complains, demonstrate to your regulator that your procedure was fair, reasonable, and applied evenhandedly, and to the extent possible is consistent with actual outcomes.