The type of storylines you get has nothing to do with the type of regular missions you run to get them. The only things that matter are the level of the agents and the faction they belong to. Other than that, they’re all drawn from the same pool.
This is actually a good thing for players running missions for standings, because you may choose the type of missions you prefer to run the first 15 missions, then do the 16th mission for an agent of any type that’s closest to the agent you want to get the storyline from.
Although it wouldn’t have answered your question, you may learn more about missions here: