We don't need to explain the potential for success that a spin-off Green Lantern: The Corps would have, since we know moviegoers love their team-ups. Strength in numbers is the reason for the Corps' existence, so it's about time Hal Jordan got some backup, and audiences got more characters to relate to.
Starting with Guy Gardner: the man also chosen as Lantern of Space Sector 2814, with Hal Jordan's proximity to Abin Sur's ship the only deciding factor (a fact Gardner never let Jordan, or anyone, forget). Gardner's constant wise-cracking would also take the responsibility off of Reynolds, freeing him to focus on the wounded side of Hal Jordan's character.
Add former marine and architect John Stewart - the Green Lantern of the Justice League animated series - and address younger viewers while including one of the all-too-few superheroes of color. If both were embraced by audiences, DC has even more options for the future. But what threat could demand the induction of two new human Lanterns?
Perhaps the Guardians' mysterious actions coincide with the disappearance of Earth's most infamous villains? Humanity had better prepare itself...