Don't have the reboot tread the same ground as the last movie. Start the movie, The Green Lantern Corps, with John, our lead character, waking up on Oa after a nightmare. The movie will essentially be an exploration of 'war', soldiers, camaraderie, responsibility, a clear mind vs a troubled mind, etc. (taking place after the first JL movie, where we were introduced to John, and his wound-up personality).
Due to Hal Jordan's disappearance, John is assigned a new loudmouther partner, Guy Gardner, and John shows him (and the audience) the basics, although John's ring seems to be 'malfunctioning'. Tomar Rae suggests that it might be psychological; that something is on his mind.
Sinestro especially gets ticked off at Guy, especially in contrast to John, who he admires; he praises John for his previous profession as a soldier; his sense of duty; etc.
Throughout the movie, John and Guy investigate matters surrounding the mysterious yellow lantern corps in their sector; chasing leads, interrogating aliens in bars, etc, etc. However, the two butt heads along the way and Guy Gardner heads back to Earth after having enough of John. We receive small snippets of John's past through flashbacks (atrocities in the war) and dialogue (becoming an architect, etc).
A lead brings John to Korugar, homeworld of the GLCorps leader Sinestro, where he discovers its enslavement, finding the missing Hal Jordan as well.
Sinestro wants John to join him, like he asked Hal, who refused. He explains that he merely wants to control things so that there is no conflict; Sinestro has lost things in the past due to war as well. John seemingly agrees, stating that he doesn't want any world to experience the atrocities of war. However, he secretly helps free Hal and the rest of Korugar. A rebellion forms to overthrow Sinestro's men on Korugar. Sinestro reveals himself as the leader of the yellow lantern corps, and orders them to attack Earth, as punishment for what John and Hal have done to his homeworld, 'dooming them to the horrors of war'.
Hal says he'll take care of Sinestro, while John heads back to Earth to defend it from the incoming Sinestro Corps.
When he returns to Earth, he searches for Guy Gardner in his home town, discovering aspects of Guy's troubled family/past. Seeing Guy able to overcome this inspires John to get over his own past. The two come to an understanding, and the two along with the rest of the corps engage in a massive battle outside Earth against the Sinestro Corps.
Hal has an epic battle with Sinestro at the end on Korguar in front of the yellow central battery and Hal is forced to throw Sinestro into the battery, killing him and deactivating the Yellow Lantern Corps.
After the battle, John meets a distraught Hal again on Oa; Sinestro really was his friend on some level. John reminds Hal of the sometimes necessary cost of war; telling Hal (and himself, more or less) that "it's okay". Hal introduces John to Sinestro's replacement, Katma Tui, the leader of the rebellion on Korugar who John saved. John welcomes her to the corps.
