I love a good western, and I might love it's derivatives the Samurai and Kung Fu master even more. The plots are formulaic, but its a great formula.
You have a master warrior who has renounced his former life. In the Kung Fu variation its because he's seen too much violence and wants to live a life of peace and mediation. For the Samurai he has been disgraced (perhaps by a former pupal who turned to evil), and for the gunslinger you have a man who has never lost a fight except to his own demons.
This former master lives a simple life in some backwards rural country where the locals regard him with derision and disdain. He has some job or attributes that reinforce the locals beliefs that he is week or stupid. However, upon seeing some innocent in trouble he reveals his power in some small way to save them. The rescued innocent then spends considerable time convincing the master to join some larger conflict between the good locals and the evil external force that threatens them. Eventually he agrees, takes up his sword (or gun, or fists) again and defeats the bad guys, or sacrifices himself to defeat the bad guys.
The greatness in this story is that we always know that the hero can defeat the bad guys, but the tension is if he can conquer himself. So its redemption and bad guy ass kicking all in one.
The problem here, is that ANH already hit all the high points of the hero story for Obi Wan. Not in as much detail as a 2 hour film about Obi Wan, but still they were all there. Crazy guy living outside of town is a master warrior, Check. Saves innocent and then is drawn out of seclusion back into the conflicts of his former life, Check. Defeats the bad guy, Check (with a nice twist).
Since the Obi Wan story is book-ended by the PT and ANH, a lot of the western formula cant work. He can't reveal his powers (especially on Tatooine), he cant get drawn into a larger conflict. Now, if you can get an Obi Wan western made, I will throw money at it, because its the best story for him. Still, what might fit cannon better is Obi Wan as a quiet assassin picking off anyone who gets too close to Luke or Leia without ever being seen (feel free to drop Professional references in to tie Natalie back to the story
). We have precedence now from Rebels that Inquisitors hunt for force sensitive kids. Its hard to imagine one sending out a stronger signal that Luke freaking Skywalker. Maybe Obi Wan decides its best if he just takes out all the Inquisitors one by one as silently as possible so they can never find Luke. They are gone by ANH, so something must have happened to them. A Munich in space maybe?