Sam Raimi came out and said that if he were to direct Spiderman 4 he’d want to use Elekto, Vulture, or even the Sinister Six. If he does the Sinister Six, then he’ll need to bring back Doc Ock (Spiderman 2) and possibly Sandman (Spiderman 3).
I love Spiderman, and I’d love to see the Sinister Six in a movie, and it can be done, but with how Raimi has presented the villains in the movies (except Venom and Green Goblin) it would be hard to imagine. The villains in Raimi’s Spiderman movies all have a redemption factor. Even in the first move Green Goblin pretended to be redeemed before getting impaled on his glider. Venom was the only one who didn’t do the I’m sorry thing before his death.
For those who think it would be impossible to bring back Doc Ock, I think if they used the AI controlling him and keeping his brain active it would keep his body from decomposing and would make him able to return. The Sandman would be difficult because he goes off into the wind, but he is still a criminal, so with the right story it might draw him back.
I guess only time will tell if Raimi will be able to tell this story, or if he’d even want to it if there wasn’t a decent centralized story to back it up.