Montreal isn't looking to add a RW right now with Dach, Anderson, Gallagher and Armia all being better options than Kapy.

If none of them gets traded away, it would be a bad move to take his caphit, including next season, for a position already filled.

Drouin/Kapanen swap isn't a terrible concept, we're just at a point where we are better with the empty slot at wing than replacing Drouin with an outside addition.
We need to shed contracts to develop our own forwards.

I don't know if this trade makes much sense for either team

I wouldnt hate the idea either but it’s probably a redundant move for both teams.

Pens would probably have to add that mid round pick too since Drouin would probably need to be retained and is expiring.

Pens can’t take on that 5.5M only moving Kappy’s contract out. And in this deal Allen is making 1M more than DeSmith and Pens are already up against the cap.

But DeSmith > Allen. Habs would get a solid NHL back-up with playoff experience for this season and next and at a cheap price. While they are figuring things out, DeSmith is a nice stop gap.