In medieval times we had the knights templar that operated essentially a banking system where they would take monies in and give out a writ (Essentially an IOU) that supposedly had a system to prevent them from being forged. So anyone that wanted to travel on the Pilgrim's road could "deposit" gold with the Templars in England, and then get gold from the Templars on the trail all the way down to Jerusalem. Never having to carry more than a couple of weeks' worth of gold needed during thier travels.
If a DM wanted, he could incorporate something like that into his game. Being S&S-based it could be something other than Knighthood based, Maybe one of the Guilds, or a group of high-level Mages, Or major Religion that organize it (Note: It's a profitable Operation, so worth it for a larger organization to do). You could make it as a set of roads that Circumnavigate the main continent of Hyperborea along the coast, with locations in the major "City's and Outposts" on the road...
Bob
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BlackKnight, AKA Sausage
Older than Dirt, Crusty, and set in my ways. Been playing TTRPGs for over 45 years...