If you want this to really work:
You are probably sending back Byfield, Clarke and Kempe, (+ draft assets, ignore that for now) which more than covers this year's McDavid salary. Kopitar rolls off the books the following year which allows for the bump on the extension contract to be absorbed, plus the cap goes up a lot.
Here's the fun part, you probably still have room to sign Marner.
So you roll next year with:
Fiala/McDavid/Marner
Turcotte/Kopitar/Laferriere
Foegele/Danault/Moore
Lee/Helenius/Thomas
If your 6 D are Doughty, Anderson, Gavrikov, Spence, Edmunson, Moverare. Goalies are Kuemper and Portillo.
Under contract today we have $21.7mm of cap according to PuckPedia. Byfield/Clarke/Kempe add up to $12.65mm in 2025-26 salary, which is a near perfect offset for McDavid's $12.5mm.
So that $21.7mm becomes ~$22mm. To sign Gavrikov @ $7.5mm, Laferriere @ $3.5mm, and Marner @ $13mm requires freeing up $2mm, which can be done by trading Moore somewhere and taking back a cheaper player or elevating someone else.
The really fun part starts in 2027-28 when Doughty's contract rolls off and you have room for an actual prime star D-man to replace him.
Okay, I'm done dreaming. But that top line would be something to watch!!