Ravinoff said:
Mysterio could be neat if his costume isn't a green onesie with a fishbowl and a purple cape.
I'd hope he
would be in his ridiculous costume. Not only because I love 'camp' Mysterio, but because the Avengers could make a big deal about it. He could hide behind his illusions for most of the film, covering himself up and such, and then when he's finally revealed, they would all stand around flabbergasted, and much hilarity can be had.
But, really, Spider-Man isn't getting a standalone MCU film, and he's unlikely to get a villain of his own in the Avenger team up movies either, because there's no space for them to add a villain with real weight to an Avenger film, and all of Spider-Man's well known rogue gallery members that could potentially stand up to the Avengers in some way either are over played already (The Goblins, with all their money and tech and such) or make no narrative sense (The Symbiotes, Genetic Mash-Up Spider-Man, etc). The best one will probably get is some second string villain (Of which Spider-Man has a fuck ton) thats only purpose during the film is to introduce Spider-Man, as he deals with them in under 3 minutes and Captain America/Black Widow looks on.