I honestly do not see McDavid playing in the Trotz system. He would probably hate it and leave when turns UFA. If you gave away too many good young key core pieces to get him and you still can't win similar to situation in Edmonton then he will repeat what Tavares did, walk as an UFA or even ask for a trade sooner.
If Isles lose Sorokin, Barzal, Dobson, Pelech, and Walhstrom plus a couple of 1sts, they will be a much weaker team and McDavid can't do all the scoring by himself, right while the other team score bunches into the Isles net. He will have to score hat tricks each game in order for Isles to win. For a generational talent, even that is too much a task.
Isles are better off to hold on to their young core and hope that they gamble and land Bedard in 2023. If Florida can find good 2nd scoring pieces in smart trades and drafts to compliment their stars, any team smart enough can do the same. You do not need to trade for a superstar because it requires you gut your team to get him.