"Because he's got a big mouth"
Fast 5 quotes aside, I do think he would bring a change of pace to the character. If John Stewart is anything like Roman Pearce, I am down. If not, I am still interested in how he would portray the character. I'm not a critic, if I like an actor in one role, to date i'll like his or her other roles, related or otherwise. It is that way with Vin Diesel, it is that way with Paul Walker, Michelle Rodriguez, Steven Seagal, Jackie Chan, Jet Li, Scarlett Johansen, Chris Hemsworth, Robert Downey Jr, and many others.