A few offer sheet notes:
You can work out a trade ahead of an offer sheet being signed, but once it's signed, your choices are limited. You can't work out a trade, for one. You either have to match (in which case you're not allowed to trade the player for 12 months), or you have to decline and take whatever compensation is laid out by the CBA.
Like I mentioned earlier, Nylander's $6.9M cap hit became well over $10M last year, because of how late he signed in the season. So if someone is signing Mitch to an offer sheet for the Auston Matthews+ level of money he's seeking sometime after the star of the season, they're going to have to have all of their draft picks, as well as $12-16M in free cap space just sitting around.
That narrows the list to a pretty small group of teams, especially when you take into consideration the teams that have their own RFA's or pending UFA's to sign. That leaves you pretty much with just the Devils ($19.8M in free space, with Hischier & Hall on the last years of their deals), Colorado ($23M, with Rantanen still needing to be signed this summer) & Ottawa (lol) as even the remotest possibilities.