I know it's probably too late to make a stories game for San Andreas at this point, but it I were to make one, I'd call it "GTA Los Santos Stories". Here's the premise:
It was the 1980s, where the Grove Street Families were founded by Sean "Sweet" Johnson and became the biggest gang in Los Santos. Now, in the early 90s, things had changed. Drugs are now introduced in the hood, undermining the Grove Street Families members. To make matters worse, Sweet's mother Beverly undergoes a heart condition, which would require a transplant in order to save her life. While being in contact with a loan shark named Black Jack, who has agreed to help the Grove Street Families clean the hood in exchange to pay him back the money Sweet loaned him, Sweet now has to work his way to earn enough money to pay back Black Jack and his mother's heart transplant at the same time while keeping his hood safe from any drug dealers, base slingers, and of course, the Grove Street Families' rivals The Ballas.
So I decided that if there was a "Stories" game based on San Andreas, I'd have the storyline somewhere around that premise so it would be more cohesive and have it set a year before the events of San Andreas.