

Idea: The second season of Lanterns could be about John and Katma Tui as partners.
At the end of the Green Lantern season, Guy warns John that the Guardians will eventually send someone if John doesn't return the ring.
And what if that someone is Katma herself?
In the comics, Katma was chosen to be Sinestro's replacement and trained John to be a Green Lantern.
One thing about her is that her people didn't see the Lanterns as heroes, but as enslavers, since Sinestro tyrannized them, making Katma be seen as an outcast. She even thought about leaving the Corps, but Hal convinced her to stay.
So... she's a character who has a connection with the three most important characters in the series. Season 2 could be about her being sent by the Guardians to watch over John. The two end up needing to ally for something bigger, and she reveals more about Sinestro's past, perhaps mentioning that she knew Hal Jordan, maybe even being mentored by him before?
And the two gradually develop a friendship and then a romance.