My thought, even if the currency is not trading at full value, it should trade for more then it is. Perhaps 80% of face value at that factions store. It'd give you an actual reason to hold onto that factions money rather then convert it at a casino, or use it at a misc wasteland store. What are your thoughts?
edit: This would also open the door to quest mods, raiding legion/ncr vaults or cash convoy? Try spending the stolen cash at the shop for full 80% value, or turn in to the opposing faction for 60% return in the other factions currency.
