I think just simply being a skin for Deadshot would be a waste of his potential. Even though they both use firearms, Deathstroke also has ninja training and also uses a sword and a staff.(the latter which NRS didn't even make apart of his moveset in the first game).
I've been thinking since Red Hood is also a pretty heavily requested character as well and his shtick is basically Deathstroke with a dagger, that NRS could give Deathstroke an almost completely new moveset that makes him less gun-centric and has him mainly using his sword and staff. That's the only way I see all three of these guys making the roster.