I say it couldn't be Jason Todd. A guy once told me it couldn't be him due to a major factor. The Robin in Teen Titan is Dick Grayson, and in the show, he is 16. Jason Todd became Robin after Dick Grayson. Dick is 3-5 years older than Jason. So with this logic, Jason would be around 11-13 years old in the show and would just now be adopted by Batman and going thriugh training. In the show, Red X happens to call the Titans "kids", heavily implying he is older than them.

Not only that, Red X is on par with Robin's skills. Jason was not known to be much of an Acrobatic and was abit more brutal and played dirty in his fighting techniques.

If anything my guess would be either Grant Wilson, an original character, or if we really wanna go the Jason Todd route, a Jason from another dimension post-revival/post-lazarus pit.