TB would clear, at minimum, $7.35m in cap space for next season (and still have the ability to squeeze a bit more in cap savings via buy out, assignment to the AHL or retention in a trade) in the scenarios I presented.
Sure, it's not the $11m that could be gained by trading Miller and Callahan separately and not taking any salary back or retaining any money but how realistic is that? If you're already thinking, as I do, that moving Callahan means some amount of retention and/or a contract coming back, then there's really little difference to justify a preference one way or the other.
It depends on whether or not we could pay an even bigger premium to get somebody to take his whole contract. It's only one year, and we have to weigh it against buying him out. The difference between 7.35 and 11 could easily be the difference between keeping and losing Anton Stralman, or some other key player. So I think the priority has to be moving Callahan's entire year's salary, even if it means we have to pay a big price. Because if we're retaining, or taking a contract back, does that have much benefit over buying him out? Considering we'd keep the asset required to move him.
Like I said, I do think the value is good here, but I think it should be a last resort. I'd rather explore separate moves. If nobody's willing to take Callahan's salary for the year, with whatever pick/prospect we can offer, then yeah, Option B becomes "move as much of his salary as possible."
Miller should be easier, I think. It's not often a team more/less gives away a 25 year-old 60ish point player signed throguh his prime. I don't think we'd have to take anybody back for him. It would be similar to a team acquiring a UFA, but on a better contract, with a somewhat minor asset (low 1st, at best, I'm thinking) going the other way.