Depends on what time period you want to set it in. If it's set when the Emperor of Japan has cut the nation off from all forein contact, then it could be just samurai and/or ninja vs the Predator, and that would be just as good.
A "Predator in the Wild West" story could take place in the Apache Nation years before the white settlers ever came to North America, and the arrival of the Predator could create some ancient native monster tales (sasquatch, wendigo, etc). Or it could take place when the white settlers are spreading across the land and the Pred is hunting both the cowboys and the natives. The Apache braves blame the deaths on a legendary monster, while the white settlers are blaming "those savage injuns." Then when the truth is discovered, they have to unite in order to survive. If they ever do this story, I'd like to see the actor who played Billy in the first movie play one of the Apache in this one.