Karlsson at 50%? Not for my team but it might be okay
To me, the Oilers would be one of the more ideal candidates to take him on.
1. They are trying to contend immediately
2. They don't have a ton of movable assets (or cap space) they can let go of to acquire someone better (and thus more expensive).
3. They have matching salaries in Foegele and Barrie.
As long as a Foegele replacement cost 1M, it would be cap-neutral and a massive improvement on Barrie for the next two seasons. It could be a problem for year 3 and 4, but by then the cap is going to increase substantially and the Oilers cap-sheet cleans up a bit. His contract would be over the same time as McDavid need a new one. (Edit: nevermind, one year longer. )
Further, Edmonton hasn't been a great "draw" for free agents, even with McDavid, so they can't really expect to get a player of Karlsson's calibre in free agency.
Edit: The other team I think should take a run is the Panthers. Trying to contend immediately, have a hole in their roster at RHD, and they have salary to send back to San Jose (Bob). Also, they're short on futures, so getting a better player/situation might not be in the cards.