So not that we know Marcus will be back and Arcade Gannon is in the game, what about his guy? http://fallout.wikia.com/wiki/Joshua_Graham
Of course, some modifications to his history would have to be made, but he seems like a very, very interesting character especially if you're playing an evil bastard.
Oh yes!
I've always thought he sounded like such an interesting character. And he's kinda like the pariah dog. He's an [censored], everybody dispises him, he's hard to come along with, pick fights with people, insults... Such a huge personality, even though it's a really bad personality. He would be the ultimate follower for an evil character... I'm planning on
trying to make an evil, elderly man who is good in all the non-combative skills, but not so much fighting, then a crazy and evil [censored] like Graham would suit well as a right hand to "deal" with problems (and you probably have to get him out of problems all the time aswell.)