I think this is the issue and these boards trades are rarely realistic.
The starting point is who could really use Marner, this is likely a competing team that has a hole at RW.
So when I hear Columbus, anaheim, etc. I just don't see why those teams who are not actively competing would trade futures for the possibility of making the playoffs. Maybe I am wrong but I just don't see it.
My first thought would be the Rangers, if Tarasenko and Kane walk they were obviously trying to address a hole at RW, having such a strong LW and solid center core, I think Marner fits like a glove. Lots of options on that roster for Toronto too