Come-from-Beyond, how difficult would it be to add a feature to the asset exchange allowing accounts to trust other accounts for a certain asset up to a specific amount? The system would have to be able to handle shifting debt balances.
Why not trusting the person himself?
If you want to help a person, lend him some money. If he is trustworthy, he will give it back to you.
If you trust someone's account, you are trusting him. The reason why this should be implemented via code in the AE is so the debt transference is automatic which allows for real-time accounting.