I'm not entirely against moving Letang. I don't think simply trading him and going in another direction slams closed the Cup window--which is already rapidly closing as is.
Marino is capable of anchoring a top pairing role right now, but I don't think we have nearly the offensive punch from the blueline without Letang. Schultz has been a shitshow for years, Petts/Dumo/JJ/Ruhwedel/Trotman/Riikola are all pretty low on the list purely when it comes to production from the blueline.
If we're dealing Letang, and I can see arguments for either side on that tbh, we'd better have a plan to inject some serious production from our defense because we're going to be woeful in that regard. I think Marino can do Letang's job defensively, but where do the points come from?
LD-Marino
Dumo-RD
Petts-Riikola
That's what you're looking at if you deal Letang, so the return better be unreal, imo. For all his warts, the guy is super important to this team. Not wholly irreplaceable, but definitely a situation where moving him probably causes more problems than it's worth. If you can land someone of Hamilton, Trouba, or Krug's caliber, you're very likely fine. But those are some seriously expensive players, and guys of that caliber are not easy to find or acquire.