See, I hate to say it, but I don't know any Gothamites that Duke can actually shine opposite of save perhaps Harper Row. He just hasn't been successful nor does he have any champions in editorial it seems, save Snyder, but even he's not doing much with him. Cass would outshine him, be more popular and have more fans in the writer's room. He'd become as much a lead as Dinah was when she was leading the JLA-- in name only. Cass would eventually take it from him like the Trinity did Dinah. He needs to be Gotham's only representative on that team if he's going to have a chance.
They work well together in Outsiders because neither has the chance to really drive the team. It's going to fall to Jeff or Tatsu, so both can just be junior members. Take that veteran level away and, well, Duke will have a lot of competition. For that reason I wouldn't have Starfire on the team either.
I was telling myself Outsiders was Duke's last chance for me to care about him and here I am giving him one, real last shot before I stop caring. I won't actively dislike him, but I'll just stop paying him mind until someone can make the guy stick. I really like that he became "Robin" as part of a movement and didn't actually properly become one because it frees him from that cycle and having to compete with the others. I want that to work. It's like Steph as Spoiler before she graduated to Robin/Batgirl. He can be his own thing and Gotham really needs that, but yeah, I'm not sure it's going to happen. Want to be wrong, though.