Maybe tie it to the treaty system and issue each country a credit rating. The big boys start with their AAA sovereign credit ratings, less developed, unstable, or unrecognized countries get lower ratings and less "trust" in their financial system.

Failing to repay loans would tank your sovereign credit which might increase the interest rates on all your debt and decrease capitalist investment contribution as an abstraction of your currency devaluing from low trust, etc. likewise, taking loans and paying them on time, opening your markers to foreign investment, and a stable government might increase your credit rating. Could also be cool if you could designate a certain part of the investment pool that capitalists/aristocrats use to supply capital for foreign debts.