I would really like to see the director focus on one villian. I think the problem with 3 was the focus on trying to introduce two new villians. I would really like to see the true darkness for the fourth installment.
What would be really nice is if they chose to exclude Mary Jane completely. Peter has to deal with the fact that she is interested in others, or has just moved on. The fickle people of new york don't really care about him anymore, and are focused on other heroes (I mean, come on, Marvel UNIVERSE. Perhaps mention that the X-men have been exposed, or that the fantasic four yadda yadda).
Peter then has to deal with his mentor (Connor) becoming a villian. It would be nice to see real development of that character. Perhaps as a side-story he could knock over the tank/cage that contains the symbiote and it could disappear within the lab. Perhaps introduce the insane asylum which houses the guy carnage takes over.
I think the inclusion of multiple villians makes the movie seem less authentic. The backstories of villians are usually explained in other comics. That makes the stories on paper work well, but when trying to introduce multiple villians you get flimsy story.
I would like to see Peter at wits end trying to help his mentor without killing him. Meanwhile he deals with the real life losses he has sustained.