Here is what I would recommend:
Focus on Peter, Harry, and Eddie. Eliminate as many superfluous characters as possible.
Start with Eddie (as a mid-to-late thirties married man) coming to work for the Bugle. He's too old to be idealistic, but he still believes that the basic rules of law and order function--there isn't a need for vigilantes.
I liked the NYC loving Spider-Man thread, so I'd put that in there, but not to have Spider-Man kiss Gwen. Just to fuel Harry's hatred (This guy gets applauded even as he covers up the blood on his hands?) and give Eddie a negative vibe. Not raging hatred, mind you, just a "this isn't how it's done and I'm uncomfortable with it."
Peter decides to publish a book of Spidey photographs to aid his financial situation and give him some leverage with JJ. JJ is naturally unhappy with this once he finds out, and sends Eddie on a Spidey smear campaign. Also, he wants Eddie to find anything he can about this new ring of thugs that have popped up, terrorists for hire. Eddie promises to do what he can.
Peter proposes to MJ and she gleefully accepts. Harry catches wind of this/happens to be present and is furious. He becomes Goblin Junior.
Enter the symbiote. I prefer the space shuttle idea (particularly since JJ's son was introduced in Spidey 2), but a meteor shower works, as long as there's a build-up of some sort. It finds/becomes attached to Spidey somehow, perhaps after combat with Harry.
Peter becomes increasingly stressed with the approaching wedding, competition from Brock, and, naturally, his best friend turning against him. Harry himself is ambivalent over his new role--the stakes and consequences are higher than he realized. Does he really want to become a killer?
Peter bonds with the symbiote, and finds Edde Brock,who's been tailing him. Destroying his film, he tells Brock to give a message to Jameson: The kid gloves are off. He's not going to fight criminals any more, he's going to break them. And if the Bugle keeps harassing him like this...well...
Fighting crime becomes a dark pleasure for Spidey as he discovers increasing levels of strength and rage he never knew he had. He takes a sample to Dr. Connors to be analyzed. Connors reveals that it is a symbiote, one that amplifies the strengths of its partner and diminishing the weaknesses. It intends to bond permanently. Peter is troubled by this, but the pros seem to outweigh the cons. He's becoming invicible. The only potential weaknesses, Connor tells him, are to loud noise and perhaps fire.
Eddie is quietly appalled that Spider-Man is taking so much control and getting away with it. Jameson has threatened to fire him for not getting the goods on the wallcrawler, and thanks to the financial situation, his wife thinks it would be a good idea for her to move to her sister's for a while. Eddie pushes himself into a frenzy, trying to find anything to use on Spider-Man. He discovers the terrorists and dangles Spder-Man as bait in front of their noses. They naturally agree to lay a tap and Spider-Man almost gets killed the in explosion. Livid, Spidey drags Eddie and the ringleader to Jameson and gets Brock fired for complicity. Eddie's wife, horrified by what he was willing to do, divorces him right there.
Harry is this close to giving up the mantle of the Goblin when Spider-Man finds him. Furious that Harry stubbornly believes him to be a killer and still rattled from that trap, he decides to show Harry how right he is...and stops within an inch of murdering his best friend. Horrified at what he's doing, he retreats to a nearby church and drives it off with the clamor of the bell. Eddie, realizing he has nothing left and thinking it's best to commit suicide, goes to the church, symbiote finds him: Venom.
Peter, back to his normal self, goes to visit Harry, who tells him he's going to destroy Peter--unravel his life until nothing's left. Eddie has learned from the symbiote that Peter is Spidey and scares MJ half to death. Spider-Man looks around the city for the monster who would do such a thing and is summarily clobbered by Venom. Venom reveals the symbiote is alive, and is quite angry at Peter for deserting it. Spidey manages to escape Venom and moves across town.
Harry, meanwhile, has recovered faster than expected thanks to te Goblin formula, and goes to visit his father's grave. He tells him that he made a vow and he intends to keep it. He sequesters himself in the lab and begins to build.
Peter visits Aunt May and finds Eddie there, ounder the pretense that he's Peter's co-worker. Peter tells Venom to stay away from his aunt, to which Venom cuts to the chase: a battle on the beach tomorrow, no holds-barred, to end it all. If the wallcrawler doesn't show, Venom mows down his friends and family. Spider-Man reluctantly agrees and they part ways.
He tells MJ what's happening and says she'd be better off with Aunt May, at the moment. They have a good-bye kiss before Peter suits up for battle.
But, naturally, on her way out the door, she is kidnapped by the Goblin. Spider-Man follows in high-speed pursuit to the Goblin's lair (warehouse, secret fortess, whatever). Harry ties MJ up, and shows Spider-Man the various incendiaries littered throughout the lair. He goes on to say that any rescue attempt, and he'll trigger them--only by the wallcrawler's suicide will he spare MJ's life. Spider-Man tries to reason with him, telling him about Venom's threat, but GG will have none of it.
They have a fight.
Venom bursts through the wall, (because he followed Spidey, naturally) and there is a smackdown to end all smackdowns between the three of them. When the fight reaches its climax, Harry accidentally triggers the bombs and the place begins to go up in flames. Spidey realizes he has to get the symbiote off Brock and destroy it--he reverts to the ploy used in ASM 312, where he tells the symbiote that he made a mistake in rejecting it and wants it back. The symbiote tries to go back to Peter , spreads itself too thin, and is destroyed in the flames. Spider-Man grabs Brock, webs him up, goes to rescue MJ...and collapses from the smoke and exhaustion. Harry, looking around him, realizes the mess he's made, and pulls everybody's @ss out of the fire, literally. But thanks to the wounds he sustained, he dies shortly thereafter. Eddie is turned over to the police, and thrown into a cell next to the newly revealed ringleader of the terrorists: Cletus Kasady.
Spidey and MJ have one of those swings, happy endings all around (well, except for Harry).
Just my suggestion. Sorry if that was too wordy.