Here is what I'd try to do. I don't think it's possible to trade Gallagher and Price unless the team retain a lot of money. And even then, so I scrapped those ideas. I try to see if there's any taker for Petry, Kulak, Armia, Hoffman but I'm not confident there will be many takers.
***
To Colorado :
Jake Allen (1 year left @ 2,875M$ after this season)
Jonathan Drouin (1 year left @ 5,5M$ after this season)
To Montréal :
Samuel Girard (5 years left @ 5M$ after this season)
Reasoning : Yes there is that chemistry history between Mack and Drouin dating their junior years. But I also think the Avalanche need extra secondary scoring and Drouin can provide just that. He's prove this year his mind is back in the game. Allen is a better option between the nets than anything they have right now. He could split the load with Kuemper.
***
To NY Rangers :
Tyler Toffoli (2 years left @ 4,25M$ after this season)
To Montréal :
Vitali Kratsov
Alexandar Georgiev
Reasoning : I read here the Rangers need an extra top 6 forward. Toffoli brings same sort of offensive power JT Miller used to bring to the Rangers, minus the drama involving him around the team. He's on a great contract. We know the situation surrounding Kratsov. I don't think the Rangers value Georgiev anymore.
***
To Edmonton :
Ben Chiarot (UFA after this season)
Artturi Lehkonen (RFA after this season)
To Montréal
2022 1st round pick
Raphael Lavoie
Reasoning : I think Chiarot is a brillant fit in Edmonton. He seems to like to play in Canada so he could re-sign there no problem. He was a monster for the team last playoff. He brings grit and toughness and he's okay offensively. Lehkonen I think has more value than people are ready to accept here, those feisty middle six forward great defensively seems to come at a premium (Coleman, Goodrow, Weise, Gaustad...).
***
To Pittsburgh :
Chris Wideman (UFA after this season)
To Montréal :
2021 4th round pick
Reasoning : Wideman could help the Penguins powerplay. He has actually been pretty good since coming over KHL even in his own zone. Could help a playoff team no problem.
Habs get this to start next season, which would be another tank year.
Caufield - Suzuki - Anderson
Hoffman - Dvorak - Kravtsov
Poehling - Evans - Gallagher
Pezzetta - Lavoie - Armia
Romanov - Petry
Girard - Savard
Guhle - Edmundson
Norlinder
Price
Georgiev