Spidey4 - Lizard and Vulture - have Doc conners study of the symbiote lead to him making a scientific breakthrough on bonding reptile dna with human dna. Not to have the symbiote involved in transformation, just to have a way that makes it seem more plausible that a college lecturer who knows Spidey suddenly has this big scientific breakthrough. Most interesting thing about lizard is that only spidey knows who he is, so have the cops, army etc all after Liz, so spidey has to fight and protect him at the same time.
Basically have the vulture in as he was in comics, just a guy with a flying outfit who is a thief, start off movie with spidey after him/fighting him , then Lizard plot kicks in and vulture returns for revenge while spidey is preoccupied with him(maybe spidey ruined his suit at start of movie, he takes time to repair and come back). really want a flying villan to go up against spidey as it will be cinematically great against the web slinging(must have scene where Vulture takes spidey way up into the clouds and drops him), Lizard covers his climbing/agility powers.
Spidey 5 - have not thought about this one really, but maybe bring in Scorpion, original origin so we can get J.J.J involved in main plot more, tricky not have his fights like Doc Ock, but Scorpion has super strength too. Maybe bring in Carnage too, symbiote from Doc conners gets loose, could be done really scary, take full advnatge of symbiote villan this time.