If he's on the line, I'd put in some squats with a pause at the bottom. I know when I first started playing, if we had to stay in a three point stance for too long my legs started to shake. Maybe he can squat with a sand bag, count 5 seconds, then explode up and throw the sandbag as high as possible. Stuff like that will also build synergy between the upper and lower body, which of course is important for a lineman.
Also, as a lineman, he'll have to take on players that already have momentum and stop them. Plyometric stuff that causes quick contraction will help with that. He could jump off a box and focus on absorbing the shock at the bottom, and also do some sort of pushups where his hands move from an elevated position to the ground in one movement, forcing his chest and arms to get used to absorbing some shock. These should also help to start strengthening his joints and connective tissue, which of course will help with injury prevention.
Of course, these are very specific things, and You program looks really great! I'm sure he'll love it and improve like crazy. I'm jealous, actually. My wife is pregnant now, and she's convinced it's a girl. I tell her to keep saying it's a girl, because I'm sure that the more she says it, the more likely it'll be a boy.