Well, Crusader Kings II: Sunset Invasion is based upon the Aztecs invading from the West. I consider that a winner, despite all plausability. (Of course, it's not the most implausible thing I've seen outside of the ASB forum. If only in the sense that any obscure European wank within the last 600 years seems 'plausible', while anything that requires a pod before the early EU-Renaciance is deemed asb.