Offersheets fail more often than not, and spark unnecessary drama between teams. They also require a lot of draft capital, and the Habs wouldn't be in a position to warrant losing those picks straight after this season.
Then there's also the fact that the Rangers and Lafrenière are trying to get a contract together right now that would pay him somewhere in the 8M$ range for multiple years. So chances are that he doesn't even make it to RFA status.
The final nail in the coffin of this idea would be that the Rangers are actually pretty okay cap-wise to match a REASONABLE offersheet for Lafrenière even if they sign Shesterkin to the close to 12M$ deal that he is reportedly looking for.
Fact of the matter is that with the rising cap it's actually easier now to find teams willing to take salary back for nothing than in the years directly post-Covid, with the flat cap. As proof, look no further than what okay-ish players with a relatively high cap-hit, like Ceci, got in exchange last Summer.
Following that logic, the Rangers could look to trade Jacob Trouba in 2025, on the last year of his current deal, and not have to pay through the nose and maybe actually get something in exchange for him.
They could also elect to keep Trouba and instead let one or both of Reilly Smith and Ryan Lindgren go as UFAs, replace them with cheap depth or prospects graduating form the AHL, and have enough for both Shesterkin's and Lafrenière's new deals.
So yeah, it was fun talking/posting about it but your scenario won't happen.
As far as trades concerning the Montreal Canadiens go, we'll get much more clarity in the next 10-15 games as to what the 2024-2025 season will be like and that will tell our management if/how they should shift their trading strategy and focus.
And as they progress through the season, our players/prospects will show their stuff in various leagues, allowing management to accumulate yet more insight regarding the prospects' likely NHL upside.
So yeah, stand pat for now. Revisit in a couple weeks/months when we have more information basically.