I actually wrote a rushed GREEN LANTERN script in two days back in 2005. It was about 130 pages, and wasn't real faithful, but it had some very faithful elements to it. There were elements of EMERALD DAWN and the idea of Parallax, and being seduced by power, but overall, it was mostly just classic Green Lantern storytelling. It's probably the most "mainstream" script I've ever written, but it still dealt with the concepts surrounding the Green Lantern Corps.
The script featured Hal Jordan (who was portrayed as being in his mid thirties) turning his life around when he found the Power Ring. The movie focused on Hal as a character, and his evolution as a person, not just in terms of his powers, but in his personal life. The script was about conquering fears, and about learning to live with fear and overcome it via willpower. It was also about the use of fear, and the seductive nature of power, and the desire for order in the face of chaos. Hal, at his base, was a man who wanted adventure, wanted to see the stars, and to become something greater than he was. He was trying to surpass his father, and in a way, to live his father's dream. He strove for this on a daily basis, with his attempts to become a space pilot, and the ring eventually afforded him that opportunity. Hal was thematically reckless, and his arc involved him taking more control over his life, in all aspects, be it his use of power, his interactions with women and other men, or his endangerment of himself. He found something to live for beyond basic adventure and ego. At first I utilized Martin Jordan's death, but decided against in my second draft. I didn't use his father's death in the first draft, because I wanted Hal Jordan's story to stand alone. I was going to add it back in in a second draft.
Carol Ferris was Hal's on again-off again love interest, and she was trying to get him to better himself (through actually firing him at one point). Her own personal arc was pretty nonexistent, which I somewhat regret. I did make her a bit more "hands-on" in terms of running Ferris Industries, and being more than just a damsel in distress (She helped figured out Sinestro's weakness and at one point, drove a yellow SUV into him). A subsequent draft was going to have her in a dogfight with Sinestro in a plane of her own.
Tom Kalmaku had a larger role than he does in Berlanti's script. He helped Hal with the GL persona, he sought to help Hal better himself and his actions (drinking, personal relations, his life's meaning), and he helpled Carol to see that Hal was at least trying to better himself.
It was a straight origin, with Hal both learning to use the ring for good himself, and then was trained by Sinestro, who eventually became the villain of the movie when Hal discovered Sinestro's actions on Korugar, and his attempts to cover it up through the use of Manhunters. Sinestro's arc was what kicked off the movie, and he served as a "cautionary" tale to the rest of the Corps. Sinestro was not nearly as black and white has he's been portrayed. He truly wanted to maintain order, and felt that people opposing his methods was a betrayal of cosmic order.
I fleshed out Kilogog, Tomar-Re and Abin Sur a bit by having them join to defeat Legion in the beginning of the script, a scene that was to foreshadow things to come, and that showed the scope of the Green Lanterns. They returned later on Oa.
I didn't put the Jordan brothers into the script, as I feared it would be too crowded, and I couldn't really find an appropriate use for them as characters in the context of the story.
There were some absolutely massive battles in Coast City, and on Oa and Korugar. The thing probably would have cost north of $200 million to make.
Abin Sur's death was related to Sinestro, and I made he and Sur brothers, which may have been a bit forced in terms of drama, but I thought worked fairly well (except in terms of how the sectors are divvied up). This gave more weight to Sinestro's quest to maintain order, as he killed his own brother to do so. The ring didn't seek out Jordan, Sur did. Abin Sur gave the ring to Hal Jordan when Hal was the closest suitable candidate for the ring upon his crash landing. Hal was out drinking and feeling sorry for himelf and musing over his failed career when Sur gave him the ring.
The Guardians were set up as a flawed government, and Hal showed them reverence, but also questioned them. It was hinted that they would have to watch him, and that he would likely be "trouble". Ganthet was a character, who sought to unlock the potential of the Green Lantern Corps in terms of compassion, beyond just power. The script opened with the Book of Oa, and an explantion of the Green Lantern Corps.
The second script would have featured Qward and the Controllers, and more Corps. action as Hal Jordan took to the stars. Star Sapphire would have been a supporting villain, and I worked Arisia, John Stewart, Guy Gardner, and some other famous GLs into the script. The third script would have featured Kyle Rayner's introduction and Hal almost succumbing to his lust for power after an act of revenge by Sinestro.