I think the main problem is that we already have a lot of gold around for everyone, mainly in Dwilight, where everyone is Lord. In some realms, like in Sirion, we have our own way to distribute gold and I can just imagine the tons of gold some old people have with them. I know because I'm used to donate a lot of it, send it to my family or just keep it around. It's usual to keep 1/2k gold in bonds with my rich characters.
However, I can imagine a situation where a Priest of a poor religion try a loan to build a temple or something like this. Or Adventurers... maybe poor Lords that wants to build up in their regions fastest than he wants to wait for a certain number of taxes. In the end, I think the continent you choose will determine much of the success or failure of this idea. Mainly because few people will care to help, in a way or another, an enemy.
There are plenty of people who could go for more gold. A new realm wanting to quickly boost infrastructure, need more RC's, or looking for a boost to their military while in war. A poor knight who wants to get gold to be able to field a big unit to impress the leadership to get a lordship. New realm or margrave wants to fund a tournament. A losing realm in war is getting strapped for gold for military and/or food. There are plenty of reasons to need a loan.
