Alright, here's my idea for cameos:
Roderick Kingsley/Vulture- Connors could spill to Pete that he is "a good friend of mine." Peter could possibly doing a paper about him ala like Dr. Octavius.
Cletus Kassidy- If Brock lives you could have him go to Ryker's and the warden tells him he'll be bunking with "Cletus Kassidy, wanted for charges of manslaughter, rape, etc..."
Quentin Beck- I still don't see how Bruce couldn't be Quentin even as a waiter. I mean Quentin could basically be a struggling stuntman trying to get work so he does these jobs that nobody really wants or cares for until he gets his big break in "4."
Mac Gargan- J.J. in the cartoon really wasn't a fan of him ad I could see a scene where he is in his office and he is looking for a bikini photoshoot spread or something frivolous other than Spider-Man on his desk, but Gargan is late with getting it to him so he shouts, "GARGAN!"