Regardless of the accounts of Polo's life, it is well established that a trading route and trading posts exhisted and should be represented in the game. Also I realize Marco Polo is dead a century before the game starts so he wouldn't appear personally in the game. I believe it's fairly well accepted that Marco Polo and his brothers did travel to China and that Marco himself lived there for 17 years. Here is an article from Encarta:
"Venetian merchants of the day traded regularly throughout the Mediterranean region. They also maintained trading posts in port cities on the Black Sea, where they obtained silk, porcelain, and other goods that came from China over the Silk Road, an ancient trade route linking China with Rome. Little is known about Marco Polo's early life, because his own account of his travels, published later in his life, is the primary source of biographical material about him. Polo probably received a fairly typical education for children of merchants at that time, learning how to read, write, and calculate.
Marco Polo's account is also the primary source of information about the travels of his father and uncle, Niccolò and Maffeo Polo, who were jewel merchants. They left Venice in 1260 on a commercial venture to the Black Sea ports of Constantinople (now Istanbul, Turkey) and Soldaia (now Sudak, Ukraine). From Soldaia they continued farther east to trading cities on the Volga River in present-day Russia. In 1262 a war broke out behind them and prevented them from returning home, so they proceeded farther east to the great Central Asian trading city of Bukhoro (in present-day Uzbekistan). After three years there they joined a diplomatic mission going to the court of Kublai Khan, the Mongol ruler of China. The khan received them warmly and expressed a desire to learn more about Christianity. He asked the Polo brothers to return to Europe and persuade the pope to send Christian scholars who could explain the religion to him. Niccolò and Maffeo journeyed back to Europe in 1269 to satisfy the khan's request.
The pope appointed two missionaries to accompany the Polos on their return to the Mongol court. The party set out in 1271, this time with Niccolò's son Marco. Soon after their departure from Acre (now 'Akko, Israel) the missionaries became concerned about hazardous conditions along the route and abandoned the embassy. The three Polos continued the journey. Judging from Marco's account, they most likely traveled overland through Armenia and Persia (now Iran) to Hormuz at the mouth of the Persian Gulf, north through Persia to the Oxus River (now Amu Darya) in Central Asia, up the Oxus to the Pamirs, across the mountains and around the southern edge of the Takla Makan Desert to Lop Nur (in present-day Xinjiang Uygur (Uighur) Autonomous Region in western China), and across the Gobi Desert. In 1275 they reached the summer court of Kublai Khan at Shangdu (about 300 km/about 200 mi north of present-day Beijing). Marco's account records that the khan warmly welcomed the party and arranged accommodations for them.
The Polos spent the next 17 years in China. Kublai Khan took an immediate liking to Marco, who was an engaging storyteller and conversationalist, and sent him on numerous diplomatic missions throughout his empire. Marco not only carried out his diplomatic assignments but also regaled the khan with interesting stories and observations about the lands he visited. His missions took him to Sichuan Province in southern China and Yunnan Province in the southwest, as well as northern Burma (now Myanmar). Marco reported that apart from entrusting him with diplomatic missions, Kublai Khan also made him governor for three years of the large commercial city of Yangzhou. Most modern scholars doubt this claim, but it is possible that Marco held some sort of post at Yangzhou, because the Mongol rulers of China routinely appointed foreign administrators to oversee the affairs of their Chinese subjects.
According to Marco's travel account, the Polos asked several times for permission to return to Europe, but Kublai Khan appreciated the visitors so much that he would not agree to their departure. In 1292, however, the khan relented and permitted the Polos to return if they would serve as escorts for a Mongol princess traveling by sea to marry the Mongol ruler of Persia. The party departed from the southern Chinese port city of Quanzhou (in present-day Fujian Province) and sailed to Sumatra, Ceylon (now Sri Lanka), southern India, and the Persian Gulf. After seeing the princess safely to Iran, the three Polos traveled overland through Tabriz to Trebizond (now Trabzon, Turkey), where they took a ship to Constantinople and then to Venice, arriving home in 1295. "
