If they trade Manson, who replaces him on the right side? I don't have an answer. I assume you do. If they trade Girard, there are tons of guys who could replace at least his role on the team. I also disagree that other teams won't value Girard. He's been playing great hockey, and not every GM is a complete idiot who only sees size. There are quite a few teams who could use a reliable puck mover like Girard, and at 5M he's very affordable.
The direct replacement is Malinski in terms of role (2nd PP option, puck mover, potential PK), and there are likely guys in free agency every year who could play that role. Also, I agree you move Colton and Wood first - Girard was third on my list of guys to move, right before Manson.
Also, I disagree that contenting teams should not trade away guys like Girard. Assuming Lindgren stays, Girard is your third LD on the depth chart. That's fantastic depth, but also a luxury. And there is nothing that says we can't take the assets we get from trading Girard and reinvest them in the team. Taking from an area of strength to address an area of weakness can often be a very smart move.
Lastly, I know my proposed defense there isn't elite, but it's not counting any free agents to push Middleton to 7, it assumes no promotions from the Eagles, and it only needs to get us to the trade deadline, when I assume if that's the group, CMac would upgrade it. Meanwhile, if we trade Manson, here's the defense:
Toews - Makar
Lindgren - Malinski?
Girard - ???
Or do we move Girard or Lindgren to their off side? Oh, and if Lindgren leaves, then we have a very, very small, soft defense group, even with Middelton in the lineup.
To be clear, I'm only advocating trading Girard if we end up in a cap crunch and it's either him/Manson or someone clearly more valuable to the team. Ideally, I'd like to keep Girard until we have a guy who steals his spot.