Well, being a breeder, as well as a pet store that buys and sells ball pythons, I personally would never buy from someone who told me they started them on ASF's.
That being said, as long as you are up front to the potential buyer about what it has been fed, then, feel free...
But, with as many picky eater balls as I've had, why even chance the fact that it could get stuck on ASF's?
My personal opinion, if you have a "normal" ball python(don't mean morph), that will eat anything, then there is no problem with switching up the diet, it's actually probably a good idea... However, if you are breeding for future sale, baby ball pythons, why would you chance that it may get stuck?
Just my .02...