If I'm understanding correctly (correct me if I'm wrong), you're arguing that the Kremlings being present in Smash Run is irrelevant to K. Rool and the "recency" arguments against him because Sakurai added the Kremlings, generic mooks from Donkey Kong Country, only because of fan request.
Then, you turn around and argue that K. Rool, despite him being far more iconic, far more popular, and being the far more fan requested leader and King of the Kremlings to be playable (people aren't asking for K. Rool to be intrusive trophy or a stage pinata; they're fan request that they want fulfilled is playability), will not be playable because the fan requests for him all of a sudden don't seem to apply to him, but only apply to the Kremlings.
Not only that, but you used Ashley and Skull Kid, two examples whom were no where near the league of K. Rool (and honestly were not only not that often requested, but were not logical choices to begin with), and Ridley, whom status has not been objectively confirmed one way or another and whose status is still ambiguous and up in the air to support this.
If the Kremlings "fan request" got them into Smash run, then K. Rool's massive fan requests for playability are also in his favor. If the Kremlings, who were no longer "relevant" and forgotten from the Donkey Kong Country franchise, made it in to the Smash Run, then it is also no longer deterrent to K. Rool as well for playability. Which is what fans are requesting.