When I'm looking for an A-plot story, I always think of Dandello. No particular recommendation because I enjoy them all. All of her longer stories have plenty of A-plot.
Re:
If anyone else is interested in this type of story I would also recommend Veritas by Shayne Terry
I LOVE Veritas, but I think of it more as an A/B mix story than I view it as primarily A-plot driven.
My longer stories tend to have much stronger A-plots, but I believe that is just the nature of longer stories. "When the Sky Falls" is a mix but I think of both "Luck and Consequences" and "The Return of Ultra Woman" as A-plot driven. Even "And the Truth Will Set You..." has a strong A-plot element even though it starts out mainly B-plot driven. (It was originally intended to be a short
)
Bob