Shattenkirk's 1.43M dead space in years 3+4 is more attractive than a Staal/Smith buyout package resulting in 2.345 in years 3+4, but you are talking about less than a million with the cap expected to go up. Every bit counts but 900K wont mean as much.
Smith alone saves 1.2 in year 2 and is 1.145 in dead cap years 3+4.
Staal, Shattenkirk & Hank off the books in summer of 21 clears over 20M - if none of them are bought out. I think that is key they get there with Buch, Chytil, Hajek, Andersson, Shesterkin, Rykov & Howden up for RFA (who knows if theyll all be around) and Kakko, Fox and Kravstov the following summer. Oh and Zibanejad will be UFA as well unless he is resigned. Gonna need every penny.
I think if you can find a way to buyout Smith alone and make a move thats the best scenario. But that wont be easy!