I think a Venom solo movie could work, even if they make one without the symbiote bonding to Spidey first. If the movie utilizes Venom as a dark mirror to Spidey, here are a few thoughts I had: (Note these are just goofy thoughts. You can pick apart, approve, *****, whatever. I dont care.)
Make Eddie a disturbed 16-year-old who deep down though a good person, just given a horrid life. In a mirror to Spideys family life, the best route to go is use the Carl Brock aspect. For those who dont know, in Venom: Lethal Protector, Spidey finds out Eddies mom died giving birth to him and because of that Carl Brock deep down resents his own son. That could easily be used for the movie; poor Eddie trying hard and harder to gain his fathers acceptance but failing again and again. When Eddie becomes Venom, he uses the symbiote to imitate Spideys powers (perhaps as an idea; Carl Brock is a Spider-Man supporter) in another desperate attempt to please his dad. However his time as Venom makes him public enemy number one for his violent attacks on criminals.
Eddies life at high school is just as bad as his family life. Hes an outcast and is often tortured but bullies, mainly by a dangerously disturbed one named Hugh Taylor (Keep reading to understand). To make matters worse, Hugh bribes teachers to turn the other way to keep his violent streak going (His dad, Orwell Taylor, is a big CEO of a military development company (Or Oscorp).
The only person whos truly nice to Eddie is Ann Weying, who he has a crush on/obsessed with. Once the symbiote comes into play, Ann becomes frightened of what Eddies turning into and tries to be his good conscious, unaware of his new friend. This leads to the symbiote developing an immense dislike for her.
On the alien symbiote, Id keep it well, an alien. It should have a voice only Eddie can hear, leading to awkward moments where people see him talking to himself. The symbiote constantly eggs Eddie into giving into his rage and desire for vengeance against his bullies. When Eddie mimics Spider-Man, the symbiote urges him into killing criminals. Heres one difference though from the comics, here, Eddie
tries to stay away from killing despite the symbiotes urging. Theres the word:
tries. When Ann tries to get through to Eddie, the symbiote (as stated before) develops a nasty dislike for her. One idea is that it even tries to kill her, not unlike a jealous lover wanting Eddie all to itself.
Villain-wise? Hugh Taylor the bully at first. He starts out as the bad guy lets say 1-3rd of the movie. At one point after becoming Venom, Eddie sees him attacking a few students and tries to stop him. Hugh however during fight either gets killed by Venom or dies by his own hand. Either or, Hughs father Orwell, out of grief and vengeance, takes six suits of experimental armor and creates the Jury out of his best men in order to hunt down Venom.
Its a thought.