I would not fire sale Kepler at all. He is still a decent player who may hit for higher average with the shift banned. His defense is rock solid and he is, by all accounts, a good clubhouse teammate.
I like a potential OF of Gallo-Buxton-Kepler. Terrific speed and range, and good to great arms. Probably best defensive OF in baseball (when Buxton plays). Gordon as backup is solid as well, and Larnach may surprise too.
If they can get good pitching for Max, sure, but not just to trade him for mediocre talent.