I thought Ultimate Venom's origin was very feasible for the big screen--and easier to do than a trip to outer space to bring back the rogue symbiote--and that the Doc Conners AND Eddie Brock's individual storylines would also support what has occured thusfar in the movies.
But it takes Spidey continuity and turns it on it's ear, so it's not acceptable to many people.
Well the Movie I had ideal is a combo...
Ultimate SpiderMan: Venom's orgins & Brock's personal life, relation to Peter & affiar to Gwen Stacy included. "Symbiote Spiderman" plot.
Venom: The origins of Scream & the other Symbiotes that bounded with Life Agents, with Carnage as their "father".
Classic Spiderman: Professor Miles Warren as a member of the Life Foundation's genetics department. Brock's issues with Spiderman. And both Gwen Stacy & her clone.
Spiderman Animated: Venom's debut & playing cat & mouse.
Spiderman game for PS: Venom's kidnap MJ scheme & the Symbiote invasion plan (With the Warren as the mastermind).
But those are good foundations to work from.
While I respect people thinking up their own plotlines, I have to firmly reject any severe tinkering with characters such as making Brock friends with Spidey, or having Kasady able to regenerate from a single cell [we have enough problems with Wolverine doing that.]
These characters have been around for a long time, and there is a big reason why they're so popular. You start changing everything around and you end up with something like the recent Catwoman-in-name-only movie that flopped so resoundingly, not even making back its advertising budget. Do we want to see that? Not me, anyways.
As far as who should play Brock, some good suggestions I have heard are David Boreanaz [not far off in looks and build] and Luke Goss [most recently seen as the baddie in Blade 2. The man is seriously hot]
For Kasady, Tim Roth would be nice. Some have suggested Zack Ward, who looks a lot like the Bagley version of Carnage, altho he might be a bit young. I have not seen him onscreen yet, so am reserving judgement till I do... I do regret Brad Dourif is a bit too old these days, he'd have been PERFECT.
I AM AGAINST CASTING AGAINST TYPE. I also think all pro wrestlers should be avoided - they tend not to act very well.
Symbiotica: Brock & Spidey hate eachother, but it's a uneasy truce when Carnage & his posse showup. And in Carnage, you forgot to add Frost from Blade{He could regeneate too, during his last moments alive}.
**
From using the Ultimate & classic storylines with my imagination, the Brock I cooked up is a relative of Peter's{His cousin} who has a grudge on Spiderman for how his life hit rock bottom.
But he uncovered his father & uncle{Peter's dad} relation to the Life Foundation & the project they were working on, the Symbiote.
There's potential. Though I really think anything involving clones (Gwen's or otherwise) should be avoided. Period.
I'd like to see the full script whenever it's close to done, if that's not a pain.