This isn't really a programming idea, but its more of an idea concerning the attitudes and organization of the players themselves. It brings several concepts with it, chief of which is;
The Traveling Village
I'm envisioning the trade guild to be a collection of people or kin who set up temporary claims wherever they plan to rest for the night or just stop travelling. Their homes would be their carts, the make-shift fences they make, and the goods they take with them. One group would be assigned to keep watch over all the goods as body guards on rotating shifts, another group would be in charge of logistics and rations, another groups would be in charge of spontaneous food procurement, and another group would be in charge of cooking the rations while people wait for the hunter-gatherers to come back with produce. Other groups would be in charge of setting up make shift homes for the others, leantos and such.
There is also the alternate idea, Traveling Village, but with waystations in between trade spots.
The Trade Guild would be a collection of people of two kinds, those who travel and those who manage inns. Imagine having a world where there'd be actual towns that serve as inns. There's be body guards, and stone mansions that provide rent. There would be purchaseable beer and provisions, even the like of company. Other players will be encouraged to start viable settlements outside the Inn-Town, but the inn would primarily serve as resting place for the Trade Caravan.
Another idea would be, The Trade Embassies;
The Trade Guild would purchase one 20*20 plot of land from every major trade spot and set up shop as a trade embassy. Like the medieval faire of the past, this is where the trade caravan shall immediately find placements of its goods. The plot must be shared among a number of people equal to the amount of shop stands they could possibly manage. They would also be in charge of the security of tehir goods and the transport of the goods brought by the caravan to their shops. While the caravan has yet to arrive, they will be required to fend for themselves through various enterprises, so shop owners should be players of considerable crafting skill so as to keep themselves economically advantageous to the village they embassy in.
already, the image of the trade caravan would be much, much more like DHL or FedEx.
A complementary idea would be, The Road Construction Service;
This is basically a group of players who offer to connect major trade spots with roads, along with clear cutting the pathways for safety.