I have to say, I love the idea of a multiverse Sinister Six. I also love the fact that most of these characters know one version/identity of who Peter Parker is. That dynamic would be interesting, as each Spiderman is very different.
I would honestly hate to be the Script writer for this though, because it just seems like a hard case to crack. I can see one or two villains at most from each franchise. Vulture, Eletro, Doctor Octopus seem legit. Green Goblin seems possible with or without the actor if he stays in his mask.
I don't think you need Venom in there. I could see an animated sequence where they go into a scene from Into the Spiderverse to meet SpiderGwen or Miles.