I won't pretend to know the mind of Erik Karlsson, but I'd be kind of surprised to learn he has a strong preference for staying in Canada. If we're ruling out the Wings because they're mediocre, it's not much of a stretch to rule out Calgary, Edmonton, Montreal, Vancouver on the same basis. Toronto and Winnipeg are Cup contenders, but if we're talking about a sign-and-trade...that could be extremely risky for either of those teams. It would almost certainly set the stage for a massive cap crunch in the very near future.
*shrug*
Looking at the Wings specifically...bleh. The more I think about Karlsson donning the Winged Wheel, the more it feels like a pipe dream. The Wings have said they won't be trading for him and I think that's the right call, whether we're talking rental or sign-and-trade. So that already puts us behind a number of teams. If we're not trading for him, we'd have to get him via free agency, which means 1) he'd have to make it to free agency in the first place and 2) we'd have to beat out probably two-thirds of the league in an epic bidding war for the ages. While the Wings do have some selling points, I doubt it'd be enough to land Karlsson.
Does that disappoint me as a Wings fan? Not really. I'm not convinced Karlsson immediately makes us a dark horse Cup contender, even if all he's costing us is money. I don't think our young players are ready for the rigors of cup contention and deep postseason runs, and I'm guessing they won't be ready for at least another couple of years. By that point, Karlsson is 30(+) years old and his body could be breaking down, given his injury history and the minutes he's played. So much of his game is elite skating...and his legs have already seen an entire career's worth of s***. That's a recipe for buyer's remorse. Seems almost inconceivable here in 2018, but I'd say his best years are probably behind him. Playing for a perennial powerhouse team could prolong his prime, but there's no reason to believe the Wings will become that kind of a team within the next few years.
Any way you slice it, Detroit doesn't make much sense as Karlsson's landing spot. IMO.