I'm no comic book expert (or even a fan), so take this with a grain of salt but...this sounds like a terrible idea. The Marvel universe (The Avengers one) makes some sense because people know who those characters are. I don't know who Spider-Man hangs out with, and don't care enough to pay to see a sequel or spinoff featuring that character.

Spider-Girl? Arachnid-Teen? Cyborg Uncle Ben?

I've frustrated myself just asking these questions. Why can't the Spider-Man people just be happy for the success of The Avengers and focus on sticking to the Spider-Man approach of a more personal story about love and alienation, occasionally with Willem Dafoe on a flying surfboard?

Sure, the last entry didn't do gangbusters, but it was pretty good. Don't bombard us with a billion characters. Avengers already does that, and they will do it better. Just be yourself, Spider-Man. It was good enough for Kirsten Dunst, who's standards are my barometer for decency.