There's many differences of opinion as to what assets the Jackets need most right now. There's logjams at D and wing, and C is already overstocked as well. That would seem to suggest goaltending is the need (especially with how Elvis is doing), but Tarasov and Greaves both look pretty good. The prospect pool is extremely deep and of high quality (top-3 in the League), so we're not searching for picks either.
About the only regularly agreed-upon constant - and even then it's only a little better than half the time - is a need for more Skilled Mentor types. Guys who can show the kids we're developing the right way to play, while taking up higher spots in the lineup so that they're actually taken seriously. Right now we've basically got Boone and that's it. We don't need the typical bottom-pairing/bottom-6 guys who are frequently thereby available; Gudbranson and Kuraly have that covered.
I'm in the camp that feels that the defense, having not performed well, would be the best place to go for an upgrade - I am absolutely craving us getting a good quality second-pairing (or better) experienced defensive defenseman. So that'd be my goal. In Seattle's case, that probably means Larsson, which I suspect is a non-starter owing to being somewhat irreplacable at the moment. Oleksiak might also work but I'm not sure he'd be enough for a Laine trade (we're not going to be selling him as anything less than a top-line scoring winger, because there's no hurry to get rid of him and no pressure).
Bringing back Bjorkstrand might also do, although that'd be more in the interest of appeasing those of us fans who wish we never lost him.