It can either be someone who's had one before (Starfire, Tempest) or one who hasn't. Feel free to give a premise and who you'd like to see writing it.
Donna Troy
I'd either focus on her job as a fashion photographer or have something like her running a shelter for runaways. I'd have Gail Simone write it.
Ryuko Orsono
I'd probably make some changes to him. I'd make him a mage who specializes in creating mystic weapons and items similar to Archer from Fate/Stay Night. This could also be a chance to explore Japanese mythology in the DCU. Kieron Gillen seems like a fine choice.
Beast Boy
A mini series of Beast Boy fighting both Titans and Doom Patrol villains and his relationships with both teams.
Those are my choices. What are yours?