Marner, imo is redundant is some respects to JG. Marner is a much better defender than JG, but offensively redundant as a perimeter player.
From watching 7 PO games, Marner would not be a change-in-culture acquisition.
I'm with the camp that would attempt to grab Tkachuk. That is the type of player needed to not only be successful but to infuse the culture change that makes CBJ a pain in the ass and ribs to play against. There are not many of those.
That's what makes McDavid such a unicorn - he's not just ultra-talented but he skates at a beyond-elite level and has the motor to take those skills wherever necessary on the ice. You don't think of McDavid as physical but watch EDM play this next series. McDavid is the Alpha Dog - EDM finally has some others around him (other than Draistl who is a unicorn in his own right) to where they are a threat every year. No doubt McDavid will never be available - the point is that if you can grab a player with both skill and motor, you do what you have to do to get that player when your roster lacks that motor. This isn't the player who puts you over the top - this is the player you MUST to have in your core to begin to move forward. Tkachuk fits that bill for me.
Culture change cannot just be at the upper management-GM-coaching level - that will take 10-15 years to result in changes on the ice. Not fast enough for most of us. That management change is needed, but it is not enough.
Culture change is needed at practice, in the room and in games - it's demanding of Fantilli, KJ, Jiricek, Mateychuk, Marchenko, etc.. on a nightly basis that it takes "balls" to be successful in the NHL long-term. To bring your A-type personality to every game, to play their individual roles as best they can without fear. It's having the bona fides to tell a JG that he needs to man up and play through the holding, clutching and grabbing, to play like the stud he is even when things aren't going right. The bona fides to challenge Boone to play even harder --- if for no other reason than so that a coach CANNOT play Boone 23 minutes a night. To challenge Z to bring more to the table. To give Elvis the BIG kick in the ass (maybe too late for that now). To challenge the coach (behind the closed door) about Boone's minutes, about the fact that Gudbranson's comments about practice last year were correct - about anything. That doesn't seem to describe Boone. He's a leader by example, he's a good soldier who keeps the company line in mind - and you need those too. But you MUST have an Alpha Dog or some combination of players that together are the Alpha Dog mentality- and CBJ lacks that and has lacked it for a while. That was a combination of Foligno, Dubinsky, maybe Seth, and maybe even Panarin (if you wanted the puck). None since.
The entire roster, except for very few, need to up the constant intensity of their game no matter what game or period or score. Intensity should not be mistaken for "hits" or "scrums" or "fights." It may be that for Olivier - but that is his role! Intensity is nothing more than playing with the belief that each player's best attributes must be brought to the table every shift. It is playing their game without fear and without stats in mind. Play your role to the max, whatever it is, and let the results follow. Boone has the motor but appears neither talented enough nor verbal/confrontational enough to get others who are inherently passive players (albeit with more talent) to increase their intensity with him. He's not the Alpha Dog - he's a pack dawg. From my seat, I see Boone being often effective in dragging his own linemates into the fray - by example and a few words. But he appears not as adept at dragging higher-talented players with him (looking at you, JG and PL) as he is in getting equally-talented or less-talented players to engage when on his line. I also see him not as effective in dragging other lines or D-men into the fray on a consistent basis. Boone keeps banging on the drum but ...no one seems to hear the beat. Too many others back off their best game when things get tough.
Marner is a wonderful player but not the Alpha Dog to cause others to intensify their game. JG is not that type of player/leader. Laine is not that. At times I am not sure Z is that (sometimes he is). But JG-Laine-Z all could be better at it, even if not their calling card. I am not suggesting jettisoning any/all of those players; CBJ (every team) needs players with their skill level - and more. They need a play-making KJ. They need JG darting all over the ice. They need Gudbranson to keep bringing energy, just wish he had more talent to add. They need Boone to just keep playing hard - on the 3rd line. Marner is the player you get when you are close, imo. CBJ is not close.
They need Fantilli to be the next Alpha Dog - but he's not ready yet and won't be for a few years - and until someone shows him how it's done.
To me, CBJ's obvious need is for an Alpha Dog, now, with high skill but also a high motor who can drag 10+ players a night with him whether those players follow organically or kicking/screaming. CBJ won't challenge for the PO's for a year or two, but that constant beat needs to start now if they want to be there after 2 years. Something has to change - that's why I favor a Tkachuk who at least from games I watch and things I read is that combatant, that Alpha Dog, who not only has the skill and intensity in his own game, but effectively DEMANDS that others bring it nightly.