Fuck it, speculation time
So we have Tim.
The green one is mentioned in Static, so Beast Boy too.
Let's just assume Static joins.
Now we're up to pure speculation.
I'd say Superboy since Cadmus was a thing in JLU would join the time eventually.
Hawk and Dove were on the JL but maybe if the Teen Titans were a thing they wouldn't be
On that subject, we have teen members of the JL like Speedy who I think would be in the Titans and Stargirl might
Maybe Zachary Zatara since Timm liked Zatanna?