There was a kid named Colin who could transform into a hulk-esque creature. He and Damian became friends in Streets of Gotham so it be cool to see him again.
I was a fan of Misfit, the teleporting batgirl fangirl Barbara tried to mentor in Birds of Prey. I thought she'd be a good foil for Damian.
I would replace the new 52 Wally West with the twins of the pre flashpoint Wally West.
Skittles was... a mess.
-Lead away by shadowy figure during the Culling and no one noticed.
-Shadowy figure was supposed to have been Raven
-Plans later changed and Skittles as Raven's companion/pet was changed to Beast Boy
-Skittles only returned right at the end of the time-travelling story where alot of crap had to be sorted out because the reboot was comming.
-Turns out shadowy figure was Skittles mom and her science buddies, who basically cured her of her inner insect, and that she would go back to being another super-scientist (no 2.890.754 in DC).
So the story of Skittles came to and end... and no one really cared
A book about Damian, Jon, young Wally and Emiko could be fun. They're basically a new Young Justice.
The only problem is that Id still want a book about the original YJ (+ Ms Martian and others) and the current TT is basically Damian's team already.