The only thing I hope they add one day is plannable heists you can do outside the story. I thought that was supposed to be one of the big pasttimes you could do to begin with but no, just in the story do they let you do them. The mechanics behind it is there since they're enabling you to do them in GTA Online with real people so the programming is definitely there that could allow it in the story with just some modifivations probablly since you'd be using your AI crew.