Felicity is likely the protagonist of the story. She could be a girl who lives in a small town. Maybe she's known for her determination and helpful nature. During the summer, she might be the one who everyone turns to when things go wrong, which is why she has the chance to save the day.
Felicity Smoak is a character created specifically for the TV series and doesn't have a presence in the comics. The show introduced her as a unique element to the story.
Well, the status of Felicity Smoak's life or death in comics isn't straightforward. Sometimes she's alive, and in certain story arcs, she might be shown as dead. It all comes down to the creative decisions of the comic writers and the direction of the particular story.
Diggle would be a great addition. He's Oliver's friend and partner, and his presence could add some interesting dynamics to their married life. He could offer advice or be there to help out in times of trouble.