Attatch the loaned gold to the character only to be used for shop transactions? Maybe...And if you take a loan on an alt you don't use? You get away with it.If OTM decided to give out loans they could easily force the player to fulfill the loans requirements. Either good collateral or force the players gold to bleed off gold, even into negatives.
Instead of player a recieving 100k gold and giving to player b and then deleting player a. Would have to put something in place to prevent that.