I loved the Teen Titans cartoon in the 2000's and it's what introduced me to them. One of the biggest let downs for me was how some of my favorite quirky villains from the show were not canon and I think it'd be fun to see them appear and get revamped like Control Freak, Mad Mod, Mumbo, and
Cinderblock just to name a few.
An idea of mine is for Dick and his old teammates to get back together like Cyborg, Starfire, Raven, and Beast Boy and at the same time Slade decides to focus his skills less on revenge and mercenary work and focus more on mentoring new talent. I like this idea because I think Slade/Deathstroke doing something that doesn't innitially involve the Titans would be interesting especially if he was actively training new allies after realizing if he was ever going to achieve his goals he'd have to be more organized and take charge.
Basically I think it'd be cool for Slade to start up a super power mercenary firm. Ultimately though I can just picture his friend Wintergreen becoming Cinderblock because in the cartoon Cinderblock seemed to be Slade's number one guy and I can see Wintergreen easily taking on that role. Besides I love the idea of Wintergreen mutating in a freak accident and wanting revenge and it driving a wedge between him and Slade like Wintergreen being less patient than Slade and getting in Slade's face about never being able to get his revenge on Grayson.
Having said that I'd love Red X to appear in main canon and not just Future State. I think a good way of doing him would be for him to just constantly troll the Robins with his identity never being revealed.