Joseph running a gigantic con on the Russian hunter was about the only way of showing a traditional (i.e. racist) Western genre depiction of Native Americans in modern times without grossly offending people. It served both as a subversive Take That! to the genre and a loving homage all in one.
The Twist raises the question of how long Maverick and Cooper have been in cahoots — maybe even throughout the entire film. At the very least, the movie practically states that Cooper was working a long con on Duvall to get into the game and take him down, perhaps with Bret's knowledge or even his help. Note this exchange at the very end:
Coop: I really enjoyed nailing that bastard (Duvall). There's just no room in poker for cheats. That's one gambler that won't be able to touch a card this side of the Mississippi. Bret: Y'know, my old pappy always used to say: "There is no more deeply moving religious experience than cheating on a cheater."
Given the amount of double-dealing and backstabbing going on, is Annabelle stealing the money just one more plot hatched together with one of them, to split the money later?
The two guns Cooper arms himself with at the tournament aren't a matched set; one is his usual Remington 1875, while the other is a smaller Single Action Army... similar to the Single Action Army "Quickdraw" Bret carries. This is the one Bret grabs from him and uses in the final shootout with Angel, neatly foreshadowing that Cooper and Maverick were working together the whole time.
