There's no reason to rush the rebuild, things are going well as is, let the young guys develop, hopefully not lose so many guys to injuries, and let things play out. Odds are Montreal have a pick in the 6-10 range, whoever they select likely needs a year or two before making the NHL.
I'd move Allen, whether that be via trade, waivers, buyout, whatever it takes, he's not bad but unless you can convince him to be the 3rd string goalie, who only plays if Monty or Primeau are hurt then I don't want him taking starts from the younger guys.
Anderson should be moved, it's not working.
Trade Gallagher, Dvorak, and Armia if you can get anything for them, but if you can't just keep them around in depth roles and see if someone makes an offer, otherwise let them run down their contracts and leave.
I wouldn't go out and try to make a big splash in free agency, although if Savard is moved Montreal should look to replace him, and personally I would go after Brett Pesce, I think he'd be an upgrade on Savard and would like to have one of the best defensive defensemen in the league on my team going forward.
If Anderson, Armia, Gallgher, and/or Dvorak are moved you have to find a replacement, whether that be someone from Laval or from another NHL team, someone has to take their spots. I think Montreal will look for a younger forward with top 6 upside, guys like Kakko, Wahlstrom, Podkolzin as examples, or maybe go bigger and try to get Zegras, Kyrou, or someone of that caliber. That being said, I really like Daniel Sprong, Jake DeBrusk and Warren Foegele if they're available via Free Agency this summer as 2nd/3rd line winger options for a 2-4 year contract at ~4-4.5 million.
The roster I've put together leaves Montreal with just shy of 18 million in cap space (assuming cap is 87 mil), with one retention spot open. If someone is willing to trade assets (picks/prospects/roster players) to dump salaries, I'd be willing to do so as long as they're only 1 (maybe 2) year contracts.
I'd let Hutson, Reinbacher, Mailloux, Mesar, Heineman, Farrell, Kidney, Perreault, Beck, Tuch, (probably forgetting someone), and whoever we draft compete for a roster spot, but don't force any of them to the NHL, and load up Laval with our prospects
I've had enough of the Josh Anderson experiment, it's not working and I don't think it will in Montreal. He's still got some value, but I doubt it's the supposed 1st+ we were offered last year, or anywhere close to that. Move up a few spots in the draft, and get his contract off the books, making room for someone else
Harris seems to be the odd man out in Montreal at the moment. Arizona have been good at getting the best out of their defensemen, and while Harris hasn't been bad he's nothing special, and maybe becomes something more in AZ. The coyotes entire NHL d-core is out of contract this summer, so there's room for him if they want him.
Nashville wouldn't be the destination for Anderson. We have a lot of younger wingers with potential so it doesn't make sense to take on someone with 3 more years left on their contract who will be 30 when next season starts