I am going to playtest Dust Devils using my Egyptian/Norse/Roman (and Greek) Western that I've been chipping away with some enthusiasm and feedback at on RPG.net.
I am thinking of changing the core rule of Dust Devils and it has me a little edgy but I think my game has a different slant than most Dust Devil games.
I am going to change the Devil Rating to a kind of Destiny(Wyrd/Ka/Fatum) Rating. The players will choose a destiny, where they see their character going and choose a number between 1 and 3 to decide how close they are to the road that leads to said destiny.
It could be a dark fate, death at the hands of a villainous "Dog-faced man" or becoming Mayor or losing their nerve and taking up farming.
Rather than a Devil in their past it is a Path to their future. It is the Fates or the Gods or Khaibit or what have you taking a hand in pushing you towards your own personal Ragnarok.
I recommend checking out the Out of the box, into the Fire (http://www.indie-rpgs.com/forum/viewtopic.php?t=3036) thread regarding Difficulty. Several folks offer some good recommendations for altering Difficulty rules so they're not so, well, terminal.
Also, changing the Devil mechanic to Fate and/or Destiny sounds fine by me. I'm working ona Dust Devils espionage "mod" right now in which I change Devil to Deathwish. Effectively, it's much the same as Devil, while yours would be a more dramatic rules change. Obviously, changing it as you've outlined lightens the mood, and gives injects some mythical potential in characters. I highly recommend consideration of how / if Destiny (or whatever) affects the "end game" for characters. See the The Road to Hell section in the Dust Devils book for details.
Matt
P.S. You also MUST have some element in the game, perhaps even the publication of the game (in whatever form) called "The Book of the Quick and the Dead" -- that phrase keeps sticking in my brain as a great Western / Egyptian combo. ;)
...or the Book of the Dead and the Quick?
I will think about the endgame.
More later.