Who can realistically offer sheet or give Marner the money he wants without screwing up their own internal cap structure?
Marner gets 11-12M from say NYI then Barzal will want 12M.
Yep, it's a major factor. There's a reason why offersheets virtually never happen, despite the media every single year screaming that the sky is falling and that it's going to be offersheet city out there.
You have to overpay to acquire a player via an offersheet. Marner's not going to sign an offersheet that's like ~5-6 years X 9M, and if he did, we would obviously just match it. So pretty much right off the bat, a team has to overpay in terms of the caphit to acquire Marner.
Then like you said, that impacts their own internal cap structure going forward. Teams with major RFAs coming due this summer or next summer include NYI (Barzal), Carolina (Aho), Calgary (Tkachuk), Ottawa (Chabot), TB (Point), Colorado (Rantanen), Buffalo (Reinhart + Dahlin), Vancouver (Petterson), etc. It's gotta be a solid 1/2 of the league that has a ~60+ point forward RFA or top 2-3 dman RFA coming up over the next 12 months.
Then on top of that, they have to give up picks as compensation. Unprotected picks too. Anything above ~10.5M means FOUR unprotected 1st rounders, which I can't imagine any team in the league would be willing to pay. Maybe a team will try to get him on a ~5 year X 10.5M, and sneak in right under the four 1st rounder threshold so that it's two unprotected 1sts + 2nd + 3rd, but that still runs the risk of messing with internal salary structures and would overall be a very risky move.