Columbus has a lot of really good young talent - I could see it being a tempting place for Hall to sign. I think there are better options, but they may be able to offer the biggest deal.
With that being said, I do think that they will go after Hall, but I also see them more as the team that is going to be taking good players who are cap casualties. For a team that signs one of Hall, Pietrangelo, Markstrom, etc.. For instance, though I still think that the Flames will keep Gaudreau even if they sign Hall, if they do not, Columbus will be able to take the entire contract without sending any cap back - lowering the overall price of the acquisition.
It is a smart move by them, but not guaranteed to pay out. Feaster was openly declaring Calgary a cap casualty team back in the day, but I guess those buyouts ruined the market. The market is hot for unloading decent players at under-valued prices right now, and they are trying to take advantage of it I think.
My guess? Calgary signs Hall, Markstrom, re-signs Brodie, re-signs Mangiapane, signs Pietrangelo - all at discounted prices - forms a super team - and then trades Lucic and Ryan for a package of picks and prospects, as Columbus obviously is helping Calgary to win because they their city also starts with a C, but they hate Chicago.

Yay Columbus!