Acquiring E. Staal would be a prototypical Sather move for sure. I wouldn't trade Stepan. I would trade Miller to make it happen, but we need to send some salary the other way, even with a Richards buyout cap space will be tight.
I'd go Brassard, Hagelin, and Fast for E. Staal. Nash or MSL has to move to the left side to make it work. A lineup of
Nash-Stepan-MSL
Pouliot-Staal-Zuccarello
Kreider-Miller-Kristo
Boyle-Moore-Carcillo
with our defense, is a contender. The only complaint I would have with that lineup is losing Hagelin and thrusting Pouliot into a top 6 role, but I suppose that all-American line could be our 2nd line most nights if they play well enough.
*DISCLAIMER* I wouldn't trade that much for Staal and his cap hit, just saying that's what it would take to make a deal.