I would have to respectfully disagree.
The Hood has always been a character that has shunned leadership roles. At his best, he's a hero, and at his worst, he's a mercenary. If a leadership role was asked of him, provided anybody would actually know him as Jason Todd and not Red Hood (and lets face it, only the Batman and Joker are ever the ones to figure out that identity, and they usually find out because Todd all but tells them), and thus know of his late-teen to adulthood.
Nightwing, as an adult, probably wouldn't fit well with the teen mystique, but you said so yourself that Jason Tood could very well be in his late teens in this particular RP. But as I said, for someone to even know that would take a ridiculous amount of detective work, and the only people who could possibly do it from the canon characters available are Robin (who's captured), and Deathstroke/Slade (who is indisposed of at the moment). I say this because I'm unsure of the detective abilities of the created characters at the moment. As far as these villains know, Todd could just be an older (though not adult aged) villain wearing a mask and choosing not to reveal himself.
Just because he is older does not necessarily mean he would take a leadership role other than 'Watch the brat that replaced me'.