I think desharnais would offset a lot for benn, subban would make up the difference and solidify their d , some may think the first would be a lottery pick, kristo is gravy for them for the habs a line of benn centering patches and cole would be hard to stop and the young olekisiak teamed with tinordi down the road would be a solid shutdown pair
here's my best shot in the "re-united and it feels so good" theme... assuming there is hockey this year (1/2 season)
conditional pick (1st if Stars make playoffs, 2nd if they don't)
Plekanec > 1/2 season of Morrow, Fraser, pick
Kaberle < Robidas
Dallas gets two Czech-mates (sorry, couldn't resist) of Jagr, more importantly they upgrade at C & add a PP skilled dman to their league-worst PP. Plekanec's 2-way game gives them much better top-9 line combo options "shielding" Roy/Benn from tough minutes vs opposition top lines without sacrificing top-9 scoring. Possibly a strong mentor for top-prospect Faska as well.
Montreal gets 2 players who fit the style of play/attitude the new leadership is trying to instill. Losing Plekanec is a huge blow, but with Galchenyuk likely NHL-ready next year, Eller ready for an expanded role, and Gomez still around, they can manage at C, short term. Also add a quality prospect & pick while creating 2M$ in cap space (in theory)