This is a weird thread. The Sedins are garbage? Ridiculous.
I don't see how Montreal could be worse by adding two thirds of a very good 2nd line. The two pieces being LW and C is actually perfect, as the only surfeit is at RW.
Provided that they don't cost too much in assets and salaries wash out, I would be very eager to find a way to make this deal as Montreal. But Plekanec and Desharnais would have to go the other way, which might not be very compelling for Vancouver, even with a modest choice of prospects, draft picks and depth players.
The Sedins would make Montreal pretty dangerous. Right now they have one explosive line (with a career 4th liner on it) and a committee of 9 or so other forwards who chip in. The Sedins with Gallagher, for example, would give Montreal a very good 2nd line and 2nd PP forward unit, and allow them to play Pacioretty on the top line. They eat minutes, play a possession game and if they get hot, then they take pressure off of Galchenyuk and Radulov.
I doubt the Sedins are available, and I doubt more they would go for cheap, at least in terms of what Montreal could offer (a bunch of salary and B level assets). So the discussion is kind of pointless. But anyone who says they wouldn't take them, even if Vancouver was doing them a big favour and taking a big discount on the return, is just talking weird, I think.