To expound upon my cycle question.... I'm wondering if there's a "trading route" that I can take with fast travel, that travels between different cities, and guarantees that every time I visit a city, the merchants in said city will have a different selection of items than when I last visited their city?

personally i like whiterun >markarth >solitude for my trade route. if you want to see new/different/resupplied items at vendors it is 48 hours in game time.