I was never a fan of 24 and haven't seen a lot of Kiefer Sutherland movies so I'm having a little bit of trouble figuring out which lines are Snake and which ones are Miller at some points in the trailer. But from what I do know is certainly Miller, Robin Atkin Downes sounds awesome. He was great in Peace Walker.
I wonder if Big Boss is really killing Chico or those children with the diamonds. For Chico, he could be trying to put pressure on a wound or maybe trying to get him to pass out for some reason, not actually die. Plus Chico is there when they're pulling that package out of Paz. And with the diamond kids, just because you see a shot of Snake shooting the gun after a shot of them doesn't mean the two actions happen one right after the other. He could be shooting at someone else, maybe enemies walking in and finding him. We've all seen movies where someone is seen doing something but it's edited in such a way that what we initially believed turns out to be wrong.