I suggest the ability to have (1) different amounts you lend, for (2) different periods. I don't have conclave so (3) if the "for a favour" could be an opinion boost if you don't have conclave. I think as well as the current modifier for "taken a loan" (4) you could add a opinion positive modifer, called "In debt to x" which basically gives the kind of feel that if someone is in debt to someone (the lannister's) their more likely to go along with that person.

The flexibility of the amount and length means that you can been a more small time lender or a big time lender lending thousands at a time. Options could mean you only see offeres between different ranges so you don't get continually bugged by the septon wanting to borrow a tenner.

I'm not planning to expanded the loaning, more complicated means more likely to break. I'll add opinions to the to do list.